initial commit

2026-03-11 16:06:00 +01:00
parent b3c69053f6
commit 5fd80e6dd6
127 changed files with 39684 additions and 0 deletions
--- a/ios_client/EncryptedChat/App/AppState.swift
+++ b/ios_client/EncryptedChat/App/AppState.swift
@@ -0,0 +1,18 @@
+import Foundation
+import SwiftUI
+
+enum ConnectionStatus: Equatable {
+    case disconnected
+    case connecting
+    case connected
+}
+
+@Observable
+final class AppState {
+    var isLoggedIn = false
+    var currentUser: User?
+    var connectionStatus: ConnectionStatus = .disconnected
+    var email: String = ""
+
+    let chatClient = ChatClient()
+}
--- a/ios_client/EncryptedChat/App/EncryptedChatApp.swift
+++ b/ios_client/EncryptedChat/App/EncryptedChatApp.swift
@@ -0,0 +1,36 @@
+import SwiftUI
+
+@main
+struct EncryptedChatApp: App {
+    @State private var appState = AppState()
+    @State private var authViewModel = AuthViewModel()
+
+    var body: some Scene {
+        WindowGroup {
+            if appState.isLoggedIn {
+                MainTabView(appState: appState)
+            } else {
+                LoginView(viewModel: authViewModel, appState: appState)
+            }
+        }
+    }
+}
+
+struct MainTabView: View {
+    var appState: AppState
+    @State private var convListVM = ConversationListVM()
+
+    var body: some View {
+        TabView {
+            ConversationListView(appState: appState, viewModel: convListVM)
+                .tabItem {
+                    Label("Chats", systemImage: "bubble.left.and.bubble.right.fill")
+                }
+
+            ProfileView(appState: appState, isOwnProfile: true)
+                .tabItem {
+                    Label("Profile", systemImage: "person.fill")
+                }
+        }
+    }
+}
--- a/ios_client/EncryptedChat/Core/ChatClient.swift
+++ b/ios_client/EncryptedChat/Core/ChatClient.swift
--- a/ios_client/EncryptedChat/Core/KeyStorage.swift
+++ b/ios_client/EncryptedChat/Core/KeyStorage.swift
@@ -0,0 +1,397 @@
+import Foundation
+import CryptoKit
+
+/// Local file storage for keys, sessions, and sender keys.
+/// Matches Python: chat_core.py key storage functions.
+///
+/// Base directory: Application Support / EncryptedChat / {email}
+/// Same file names as Python client for cross-platform compatibility.
+enum KeyStorage {
+
+    // MARK: - Base Directory
+
+    /// Get or create the key storage directory for a user
+    static func getKeyDir(email: String) throws -> URL {
+        let appSupport = FileManager.default.urls(for: .applicationSupportDirectory, in: .userDomainMask).first!
+        let dir = appSupport.appendingPathComponent("EncryptedChat").appendingPathComponent(email)
+        try FileManager.default.createDirectory(at: dir, withIntermediateDirectories: true)
+        // iOS file protection
+        try (dir as NSURL).setResourceValue(URLFileProtection.complete, forKey: .fileProtectionKey)
+        return dir
+    }
+
+    // MARK: - RSA Keys
+
+    /// Save RSA keypair
+    static func saveRSAKeys(email: String, privateKey: SecKey, publicKey: SecKey, password: Data? = nil) throws {
+        let dir = try getKeyDir(email: email)
+        let privData = try RSACrypto.serializePrivateKey(privateKey, password: password)
+        let pubData = try RSACrypto.serializePublicKey(publicKey)
+        try writeProtected(privData, to: dir.appendingPathComponent("private.pem"))
+        try pubData.write(to: dir.appendingPathComponent("public.pem"))
+    }
+
+    /// Load RSA keypair. Returns (private, public, error).
+    static func loadRSAKeys(email: String, password: Data? = nil) -> (SecKey?, SecKey?, String?) {
+        guard let dir = try? getKeyDir(email: email) else {
+            return (nil, nil, "Cannot access key directory")
+        }
+        let privPath = dir.appendingPathComponent("private.pem")
+        let pubPath = dir.appendingPathComponent("public.pem")
+
+        guard FileManager.default.fileExists(atPath: privPath.path) else {
+            return (nil, nil, "No local keys found.")
+        }
+
+        guard let privData = try? Data(contentsOf: privPath),
+              let pubData = try? Data(contentsOf: pubPath) else {
+            return (nil, nil, "Cannot read key files.")
+        }
+
+        do {
+            let privateKey = try RSACrypto.loadPrivateKey(privData, password: password)
+            let publicKey = try RSACrypto.loadPublicKey(pubData)
+            return (privateKey, publicKey, nil)
+        } catch {
+            // Try without password (unencrypted)
+            do {
+                let privateKey = try RSACrypto.loadPrivateKey(privData, password: nil)
+                let publicKey = try RSACrypto.loadPublicKey(pubData)
+                // Re-save with password if provided
+                if let password = password {
+                    try? saveRSAKeys(email: email, privateKey: privateKey, publicKey: publicKey, password: password)
+                }
+                return (privateKey, publicKey, nil)
+            } catch {
+                return (nil, nil, "Invalid or missing password.")
+            }
+        }
+    }
+
+    // MARK: - Identity Keys (Ed25519)
+
+    static func saveIdentityKeys(
+        email: String,
+        privateKey: Curve25519.Signing.PrivateKey,
+        publicKey: Curve25519.Signing.PublicKey,
+        password: Data? = nil
+    ) throws {
+        let dir = try getKeyDir(email: email)
+        let privData = try Ed25519Crypto.serializePrivate(privateKey, password: password)
+        let pubData = Ed25519Crypto.serializePublic(publicKey)
+        try writeProtected(privData, to: dir.appendingPathComponent("identity_private.bin"))
+        try pubData.write(to: dir.appendingPathComponent("identity_public.bin"))
+    }
+
+    static func loadIdentityKeys(
+        email: String,
+        password: Data? = nil
+    ) -> (Curve25519.Signing.PrivateKey?, Curve25519.Signing.PublicKey?) {
+        guard let dir = try? getKeyDir(email: email) else { return (nil, nil) }
+        let privPath = dir.appendingPathComponent("identity_private.bin")
+        let pubPath = dir.appendingPathComponent("identity_public.bin")
+
+        guard FileManager.default.fileExists(atPath: privPath.path),
+              let privData = try? Data(contentsOf: privPath),
+              let pubData = try? Data(contentsOf: pubPath) else {
+            return (nil, nil)
+        }
+
+        do {
+            let priv = try Ed25519Crypto.loadPrivate(privData, password: password)
+            let pub = try Ed25519Crypto.loadPublic(pubData)
+            return (priv, pub)
+        } catch {
+            return (nil, nil)
+        }
+    }
+
+    // MARK: - Signed Pre-Key
+
+    static func saveSPK(email: String, privateKey: Curve25519.KeyAgreement.PrivateKey, spkId: String) throws {
+        let dir = try getKeyDir(email: email)
+        try writeProtected(X25519Crypto.serializePrivate(privateKey), to: dir.appendingPathComponent("spk_private.bin"))
+        try spkId.write(to: dir.appendingPathComponent("spk_id.txt"), atomically: true, encoding: .utf8)
+    }
+
+    static func loadSPK(email: String) -> (Curve25519.KeyAgreement.PrivateKey?, String?) {
+        guard let dir = try? getKeyDir(email: email) else { return (nil, nil) }
+        let privPath = dir.appendingPathComponent("spk_private.bin")
+        let idPath = dir.appendingPathComponent("spk_id.txt")
+
+        guard FileManager.default.fileExists(atPath: privPath.path),
+              let privData = try? Data(contentsOf: privPath),
+              let priv = try? X25519Crypto.loadPrivate(privData) else {
+            return (nil, nil)
+        }
+        let spkId = (try? String(contentsOf: idPath, encoding: .utf8))?.trimmed ?? ""
+        return (priv, spkId)
+    }
+
+    // MARK: - Previous SPK (Grace Period)
+
+    static func savePrevSPK(email: String, privateKey: Curve25519.KeyAgreement.PrivateKey, spkId: String) throws {
+        let dir = try getKeyDir(email: email)
+        try writeProtected(X25519Crypto.serializePrivate(privateKey), to: dir.appendingPathComponent("prev_spk_private.bin"))
+        try spkId.write(to: dir.appendingPathComponent("prev_spk_id.txt"), atomically: true, encoding: .utf8)
+    }
+
+    static func loadPrevSPK(email: String) -> (Curve25519.KeyAgreement.PrivateKey?, String?) {
+        guard let dir = try? getKeyDir(email: email) else { return (nil, nil) }
+        let privPath = dir.appendingPathComponent("prev_spk_private.bin")
+        let idPath = dir.appendingPathComponent("prev_spk_id.txt")
+
+        guard FileManager.default.fileExists(atPath: privPath.path),
+              let privData = try? Data(contentsOf: privPath),
+              let priv = try? X25519Crypto.loadPrivate(privData) else {
+            return (nil, nil)
+        }
+        let spkId = (try? String(contentsOf: idPath, encoding: .utf8))?.trimmed ?? ""
+        return (priv, spkId)
+    }
+
+    // MARK: - One-Time Pre-Keys
+
+    static func saveOPKPrivate(email: String, opkId: String, privateKey: Curve25519.KeyAgreement.PrivateKey) throws {
+        let dir = try getKeyDir(email: email).appendingPathComponent("opk_private")
+        try FileManager.default.createDirectory(at: dir, withIntermediateDirectories: true)
+        try writeProtected(X25519Crypto.serializePrivate(privateKey), to: dir.appendingPathComponent("\(opkId).bin"))
+    }
+
+    static func loadOPKPrivate(email: String, opkId: String) -> Curve25519.KeyAgreement.PrivateKey? {
+        guard let dir = try? getKeyDir(email: email) else { return nil }
+        let path = dir.appendingPathComponent("opk_private").appendingPathComponent("\(opkId).bin")
+        guard let data = try? Data(contentsOf: path) else { return nil }
+        return try? X25519Crypto.loadPrivate(data)
+    }
+
+    static func deleteOPKPrivate(email: String, opkId: String) {
+        guard let dir = try? getKeyDir(email: email) else { return }
+        let path = dir.appendingPathComponent("opk_private").appendingPathComponent("\(opkId).bin")
+        try? FileManager.default.removeItem(at: path)
+    }
+
+    // MARK: - Device ID
+
+    static func saveDeviceId(email: String, deviceId: String) throws {
+        let dir = try getKeyDir(email: email)
+        try writeProtected(Data(deviceId.utf8), to: dir.appendingPathComponent("device_id.txt"))
+    }
+
+    static func loadDeviceId(email: String) -> String? {
+        guard let dir = try? getKeyDir(email: email) else { return nil }
+        let path = dir.appendingPathComponent("device_id.txt")
+        guard let data = try? Data(contentsOf: path) else { return nil }
+        let str = String(data: data, encoding: .utf8)?.trimmed
+        return (str?.isEmpty ?? true) ? nil : str
+    }
+
+    // MARK: - Sessions (Double Ratchet)
+
+    static func saveSession(
+        email: String,
+        peerUserId: String,
+        ratchet: DoubleRatchet,
+        localKey: Data? = nil,
+        peerDeviceId: String? = nil
+    ) throws {
+        let dir = try getKeyDir(email: email).appendingPathComponent("sessions")
+        try FileManager.default.createDirectory(at: dir, withIntermediateDirectories: true)
+
+        let filename: String
+        if let deviceId = peerDeviceId {
+            filename = "\(peerUserId)_\(deviceId).bin"
+        } else {
+            filename = "\(peerUserId).bin"
+        }
+
+        var data = try ratchet.exportState()
+        if let localKey = localKey {
+            data = try CryptoUtils.encryptLocal(data, key: localKey)
+        }
+        try writeProtected(data, to: dir.appendingPathComponent(filename))
+    }
+
+    static func loadSession(
+        email: String,
+        peerUserId: String,
+        localKey: Data? = nil,
+        peerDeviceId: String? = nil
+    ) -> DoubleRatchet? {
+        guard let dir = try? getKeyDir(email: email) else { return nil }
+        let sessionsDir = dir.appendingPathComponent("sessions")
+
+        let filename: String
+        if let deviceId = peerDeviceId {
+            filename = "\(peerUserId)_\(deviceId).bin"
+        } else {
+            filename = "\(peerUserId).bin"
+        }
+
+        let path = sessionsDir.appendingPathComponent(filename)
+        return loadSessionFile(path, localKey: localKey)
+    }
+
+    static func deleteSession(email: String, peerUserId: String, peerDeviceId: String? = nil) {
+        guard let dir = try? getKeyDir(email: email) else { return }
+        let sessionsDir = dir.appendingPathComponent("sessions")
+
+        if let deviceId = peerDeviceId {
+            let path = sessionsDir.appendingPathComponent("\(peerUserId)_\(deviceId).bin")
+            try? FileManager.default.removeItem(at: path)
+        } else {
+            // Delete all sessions for this user
+            if let files = try? FileManager.default.contentsOfDirectory(atPath: sessionsDir.path) {
+                for file in files where file.hasPrefix(peerUserId) {
+                    try? FileManager.default.removeItem(at: sessionsDir.appendingPathComponent(file))
+                }
+            }
+        }
+    }
+
+    private static func loadSessionFile(_ path: URL, localKey: Data?) -> DoubleRatchet? {
+        guard let raw = try? Data(contentsOf: path) else { return nil }
+
+        if let localKey = localKey {
+            // Try encrypted first
+            if let decrypted = try? CryptoUtils.decryptLocal(raw, key: localKey) {
+                return try? DoubleRatchet.importState(decrypted)
+            }
+            // Fallback: plaintext (transparent migration)
+            if let ratchet = try? DoubleRatchet.importState(raw) {
+                // Re-save encrypted
+                try? writeProtected(CryptoUtils.encryptLocal(try ratchet.exportState(), key: localKey), to: path)
+                return ratchet
+            }
+            return nil
+        }
+
+        return try? DoubleRatchet.importState(raw)
+    }
+
+    // MARK: - Sender Keys
+
+    static func saveSenderKeyState(
+        email: String,
+        convId: String,
+        state: SenderKeyState,
+        localKey: Data? = nil
+    ) throws {
+        let dir = try getKeyDir(email: email).appendingPathComponent("sender_keys")
+        try FileManager.default.createDirectory(at: dir, withIntermediateDirectories: true)
+
+        var data = state.exportState()
+        if let localKey = localKey {
+            data = try CryptoUtils.encryptLocal(data, key: localKey)
+        }
+        try writeProtected(data, to: dir.appendingPathComponent("\(convId).bin"))
+    }
+
+    static func loadSenderKeyState(
+        email: String,
+        convId: String,
+        localKey: Data? = nil
+    ) -> SenderKeyState? {
+        guard let dir = try? getKeyDir(email: email) else { return nil }
+        let path = dir.appendingPathComponent("sender_keys").appendingPathComponent("\(convId).bin")
+        guard let raw = try? Data(contentsOf: path) else { return nil }
+
+        if let localKey = localKey {
+            if let decrypted = try? CryptoUtils.decryptLocal(raw, key: localKey) {
+                return try? SenderKeyState.importState(decrypted)
+            }
+            // Plaintext fallback
+            if let state = try? SenderKeyState.importState(raw) {
+                try? writeProtected(CryptoUtils.encryptLocal(state.exportState(), key: localKey), to: path)
+                return state
+            }
+            return nil
+        }
+
+        return try? SenderKeyState.importState(raw)
+    }
+
+    static func deleteSenderKeyState(email: String, convId: String) {
+        guard let dir = try? getKeyDir(email: email) else { return }
+        let path = dir.appendingPathComponent("sender_keys").appendingPathComponent("\(convId).bin")
+        try? FileManager.default.removeItem(at: path)
+    }
+
+    // MARK: - Received Sender Keys
+
+    static func saveRecvSenderKey(
+        email: String,
+        convId: String,
+        senderId: String,
+        senderDeviceId: String,
+        state: SenderKeyState,
+        localKey: Data? = nil
+    ) throws {
+        let dir = try getKeyDir(email: email).appendingPathComponent("sender_keys_recv")
+        try FileManager.default.createDirectory(at: dir, withIntermediateDirectories: true)
+
+        var data = state.exportState()
+        if let localKey = localKey {
+            data = try CryptoUtils.encryptLocal(data, key: localKey)
+        }
+        try writeProtected(data, to: dir.appendingPathComponent("\(convId)_\(senderId)_\(senderDeviceId).bin"))
+    }
+
+    static func loadRecvSenderKey(
+        email: String,
+        convId: String,
+        senderId: String,
+        senderDeviceId: String,
+        localKey: Data? = nil
+    ) -> SenderKeyState? {
+        guard let dir = try? getKeyDir(email: email) else { return nil }
+        let path = dir.appendingPathComponent("sender_keys_recv").appendingPathComponent("\(convId)_\(senderId)_\(senderDeviceId).bin")
+        guard let raw = try? Data(contentsOf: path) else { return nil }
+
+        if let localKey = localKey {
+            if let decrypted = try? CryptoUtils.decryptLocal(raw, key: localKey) {
+                return try? SenderKeyState.importState(decrypted)
+            }
+            if let state = try? SenderKeyState.importState(raw) {
+                try? writeProtected(CryptoUtils.encryptLocal(state.exportState(), key: localKey), to: path)
+                return state
+            }
+            return nil
+        }
+
+        return try? SenderKeyState.importState(raw)
+    }
+
+    static func deleteRecvSenderKeys(email: String, convId: String) {
+        guard let dir = try? getKeyDir(email: email) else { return }
+        let recvDir = dir.appendingPathComponent("sender_keys_recv")
+        guard let files = try? FileManager.default.contentsOfDirectory(atPath: recvDir.path) else { return }
+        for file in files where file.hasPrefix(convId) {
+            try? FileManager.default.removeItem(at: recvDir.appendingPathComponent(file))
+        }
+    }
+
+    // MARK: - Favorites
+
+    static func saveFavorites(email: String, favorites: Set<String>) throws {
+        let dir = try getKeyDir(email: email)
+        let data = try JSONSerialization.data(withJSONObject: Array(favorites))
+        try data.write(to: dir.appendingPathComponent("favorites.json"))
+    }
+
+    static func loadFavorites(email: String) -> Set<String> {
+        guard let dir = try? getKeyDir(email: email) else { return [] }
+        let path = dir.appendingPathComponent("favorites.json")
+        guard let data = try? Data(contentsOf: path),
+              let array = try? JSONSerialization.jsonObject(with: data) as? [String] else {
+            return []
+        }
+        return Set(array)
+    }
+
+    // MARK: - Helpers
+
+    private static func writeProtected(_ data: Data, to url: URL) throws {
+        try data.write(to: url, options: .completeFileProtection)
+    }
+}
--- a/ios_client/EncryptedChat/Core/MessageCache.swift
+++ b/ios_client/EncryptedChat/Core/MessageCache.swift
@@ -0,0 +1,65 @@
+import Foundation
+
+/// Encrypted local message cache.
+/// Matches Python: chat_core.py message cache (message_cache/{conv_id}.json)
+enum MessageCache {
+
+    /// Save messages for a conversation (encrypted with local storage key)
+    static func save(email: String, convId: String, messages: [[String: Any]], cacheKey: Data?) throws {
+        let dir = try KeyStorage.getKeyDir(email: email).appendingPathComponent("message_cache")
+        try FileManager.default.createDirectory(at: dir, withIntermediateDirectories: true)
+
+        let jsonData = try JSONSerialization.data(withJSONObject: messages)
+
+        let dataToWrite: Data
+        if let cacheKey = cacheKey {
+            dataToWrite = try CryptoUtils.encryptLocal(jsonData, key: cacheKey)
+        } else {
+            dataToWrite = jsonData
+        }
+
+        try dataToWrite.write(to: dir.appendingPathComponent("\(convId).json"), options: .completeFileProtection)
+    }
+
+    /// Load messages for a conversation
+    static func load(email: String, convId: String, cacheKey: Data?) -> [[String: Any]]? {
+        guard let dir = try? KeyStorage.getKeyDir(email: email) else { return nil }
+        let path = dir.appendingPathComponent("message_cache").appendingPathComponent("\(convId).json")
+        guard let raw = try? Data(contentsOf: path) else { return nil }
+
+        let jsonData: Data
+        if let cacheKey = cacheKey {
+            if let decrypted = try? CryptoUtils.decryptLocal(raw, key: cacheKey) {
+                jsonData = decrypted
+            } else {
+                // Plaintext fallback (migration)
+                jsonData = raw
+            }
+        } else {
+            jsonData = raw
+        }
+
+        return try? JSONSerialization.jsonObject(with: jsonData) as? [[String: Any]]
+    }
+
+    /// Search messages in a conversation
+    static func search(email: String, convId: String, query: String, cacheKey: Data?) -> [[String: Any]] {
+        guard let messages = load(email: email, convId: convId, cacheKey: cacheKey) else {
+            return []
+        }
+        let lowerQuery = query.lowercased()
+        return messages.filter { msg in
+            if let text = msg["text"] as? String, text.lowercased().contains(lowerQuery) {
+                return true
+            }
+            return false
+        }
+    }
+
+    /// Delete cache for a conversation
+    static func delete(email: String, convId: String) {
+        guard let dir = try? KeyStorage.getKeyDir(email: email) else { return }
+        let path = dir.appendingPathComponent("message_cache").appendingPathComponent("\(convId).json")
+        try? FileManager.default.removeItem(at: path)
+    }
+}
--- a/ios_client/EncryptedChat/Crypto/CryptoErrors.swift
+++ b/ios_client/EncryptedChat/Crypto/CryptoErrors.swift
@@ -0,0 +1,95 @@
+import Foundation
+
+enum CryptoError: Error, LocalizedError {
+    case invalidBase64
+    case invalidHex
+    case invalidKeyData(String)
+    case invalidSignature
+    case signatureVerificationFailed
+    case encryptionFailed(String)
+    case decryptionFailed(String)
+    case invalidECP1Format
+    case pbkdf2Failed
+    case rsaKeyGenerationFailed
+    case rsaOperationFailed(String)
+    case x3dhFailed(String)
+    case ratchetError(String)
+    case senderKeyError(String)
+    case maxSkipExceeded
+    case duplicateMessage
+    case invalidHeader(String)
+    case stateImportFailed(String)
+    case keyConversionFailed(String)
+
+    var errorDescription: String? {
+        switch self {
+        case .invalidBase64: return "Invalid base64 encoding"
+        case .invalidHex: return "Invalid hex encoding"
+        case .invalidKeyData(let msg): return "Invalid key data: \(msg)"
+        case .invalidSignature: return "Invalid signature format"
+        case .signatureVerificationFailed: return "Signature verification failed"
+        case .encryptionFailed(let msg): return "Encryption failed: \(msg)"
+        case .decryptionFailed(let msg): return "Decryption failed: \(msg)"
+        case .invalidECP1Format: return "Invalid ECP1 key format"
+        case .pbkdf2Failed: return "PBKDF2 key derivation failed"
+        case .rsaKeyGenerationFailed: return "RSA key generation failed"
+        case .rsaOperationFailed(let msg): return "RSA operation failed: \(msg)"
+        case .x3dhFailed(let msg): return "X3DH failed: \(msg)"
+        case .ratchetError(let msg): return "Ratchet error: \(msg)"
+        case .senderKeyError(let msg): return "Sender key error: \(msg)"
+        case .maxSkipExceeded: return "Maximum message skip exceeded"
+        case .duplicateMessage: return "Duplicate message detected"
+        case .invalidHeader(let msg): return "Invalid header: \(msg)"
+        case .stateImportFailed(let msg): return "State import failed: \(msg)"
+        case .keyConversionFailed(let msg): return "Key conversion failed: \(msg)"
+        }
+    }
+}
+
+enum NetworkError: Error, LocalizedError {
+    case notConnected
+    case connectionFailed(String)
+    case timeout
+    case serverError(String)
+    case protocolError(String)
+    case messageTooLarge
+    case invalidResponse(String)
+    case authenticationFailed(String)
+    case alreadyConnected
+
+    var errorDescription: String? {
+        switch self {
+        case .notConnected: return "Not connected to server"
+        case .connectionFailed(let msg): return "Connection failed: \(msg)"
+        case .timeout: return "Request timed out"
+        case .serverError(let msg): return "Server error: \(msg)"
+        case .protocolError(let msg): return "Protocol error: \(msg)"
+        case .messageTooLarge: return "Message exceeds maximum size"
+        case .invalidResponse(let msg): return "Invalid response: \(msg)"
+        case .authenticationFailed(let msg): return "Authentication failed: \(msg)"
+        case .alreadyConnected: return "Already connected"
+        }
+    }
+}
+
+enum ChatError: Error, LocalizedError {
+    case notLoggedIn
+    case conversationNotFound
+    case membershipRequired
+    case permissionDenied(String)
+    case operationFailed(String)
+    case fileError(String)
+    case invalidData(String)
+
+    var errorDescription: String? {
+        switch self {
+        case .notLoggedIn: return "Not logged in"
+        case .conversationNotFound: return "Conversation not found"
+        case .membershipRequired: return "Must be a member of this conversation"
+        case .permissionDenied(let msg): return "Permission denied: \(msg)"
+        case .operationFailed(let msg): return "Operation failed: \(msg)"
+        case .fileError(let msg): return "File error: \(msg)"
+        case .invalidData(let msg): return "Invalid data: \(msg)"
+        }
+    }
+}
--- a/ios_client/EncryptedChat/Crypto/CryptoUtils.swift
+++ b/ios_client/EncryptedChat/Crypto/CryptoUtils.swift
@@ -0,0 +1,196 @@
+import Foundation
+import CryptoKit
+
+/// Core cryptographic utilities: AES-GCM, HKDF, KDF helpers
+enum CryptoUtils {
+
+    // MARK: - AES-256-GCM
+
+    /// Encrypt with AES-256-GCM. Returns (key, nonce, ciphertext, tag) — all as Data.
+    /// If key is nil, generates a random 256-bit key.
+    /// Matches Python: aes_encrypt(plaintext, key=None)
+    static func aesEncrypt(_ plaintext: Data, key: Data? = nil) throws -> (key: Data, nonce: Data, ciphertext: Data, tag: Data) {
+        let keyData = key ?? Data.randomBytes(32)
+        let symmetricKey = SymmetricKey(data: keyData)
+        let nonceData = Data.randomBytes(12)
+        let gcmNonce = try AES.GCM.Nonce(data: nonceData)
+
+        let sealedBox = try AES.GCM.seal(plaintext, using: symmetricKey, nonce: gcmNonce)
+
+        return (
+            key: keyData,
+            nonce: nonceData,
+            ciphertext: Data(sealedBox.ciphertext),
+            tag: Data(sealedBox.tag)
+        )
+    }
+
+    /// Decrypt with AES-256-GCM.
+    /// Matches Python: aes_decrypt(key, nonce, ciphertext, tag)
+    static func aesDecrypt(key: Data, nonce: Data, ciphertext: Data, tag: Data) throws -> Data {
+        let symmetricKey = SymmetricKey(data: key)
+        let gcmNonce = try AES.GCM.Nonce(data: nonce)
+
+        let sealedBox = try AES.GCM.SealedBox(
+            nonce: gcmNonce,
+            ciphertext: ciphertext,
+            tag: tag
+        )
+
+        do {
+            return try AES.GCM.open(sealedBox, using: symmetricKey)
+        } catch {
+            throw CryptoError.decryptionFailed("AES-GCM decryption failed")
+        }
+    }
+
+    /// Encrypt with AES-256-GCM using AAD. Returns ciphertext with tag appended.
+    /// Used by Double Ratchet and Sender Keys.
+    static func aesGcmEncrypt(_ plaintext: Data, key: Data, nonce: Data, aad: Data) throws -> Data {
+        let symmetricKey = SymmetricKey(data: key)
+        let gcmNonce = try AES.GCM.Nonce(data: nonce)
+
+        let sealedBox = try AES.GCM.seal(
+            plaintext,
+            using: symmetricKey,
+            nonce: gcmNonce,
+            authenticating: aad
+        )
+
+        // Return ciphertext + tag concatenated (matches Python AESGCM.encrypt)
+        return Data(sealedBox.ciphertext) + Data(sealedBox.tag)
+    }
+
+    /// Decrypt AES-256-GCM with AAD. Input ciphertext has tag appended (last 16 bytes).
+    static func aesGcmDecrypt(_ ctWithTag: Data, key: Data, nonce: Data, aad: Data) throws -> Data {
+        guard ctWithTag.count >= 16 else {
+            throw CryptoError.decryptionFailed("Ciphertext too short")
+        }
+
+        let ct = ctWithTag.prefix(ctWithTag.count - 16)
+        let tag = ctWithTag.suffix(16)
+
+        let symmetricKey = SymmetricKey(data: key)
+        let gcmNonce = try AES.GCM.Nonce(data: nonce)
+
+        let sealedBox = try AES.GCM.SealedBox(
+            nonce: gcmNonce,
+            ciphertext: ct,
+            tag: tag
+        )
+
+        do {
+            return try AES.GCM.open(sealedBox, using: symmetricKey, authenticating: aad)
+        } catch {
+            throw CryptoError.decryptionFailed("AES-GCM decryption with AAD failed")
+        }
+    }
+
+    // MARK: - HKDF
+
+    /// HKDF-SHA256 key derivation.
+    /// Matches Python: hkdf_derive(input_key, salt, info, length=32)
+    static func hkdfDerive(inputKey: Data, salt: Data, info: Data, length: Int = 32) -> Data {
+        let symmetricKey = SymmetricKey(data: inputKey)
+        let derived = HKDF<SHA256>.deriveKey(
+            inputKeyMaterial: symmetricKey,
+            salt: salt,
+            info: info,
+            outputByteCount: length
+        )
+        return derived.withUnsafeBytes { Data($0) }
+    }
+
+    // MARK: - KDF for Double Ratchet
+
+    /// Root key KDF. Returns (newRootKey, chainKey).
+    /// HKDF with rootKey as salt and DH output as input. Derives 64 bytes, split in half.
+    /// Matches Python: kdf_rk(root_key, dh_output)
+    static func kdfRK(rootKey: Data, dhOutput: Data) -> (newRootKey: Data, chainKey: Data) {
+        let derived = hkdfDerive(
+            inputKey: dhOutput,
+            salt: rootKey,
+            info: Data(Constants.rootKeyInfo.utf8),
+            length: 64
+        )
+        return (derived.prefix(32), Data(derived.suffix(32)))
+    }
+
+    /// Chain key KDF. Returns (newChainKey, messageKey).
+    /// HMAC-SHA256: messageKey = HMAC(chainKey, 0x01), newChainKey = HMAC(chainKey, 0x02)
+    /// Matches Python: kdf_ck(chain_key)
+    static func kdfCK(chainKey: Data) -> (newChainKey: Data, messageKey: Data) {
+        let symmetricKey = SymmetricKey(data: chainKey)
+        let messageKey = Data(HMAC<SHA256>.authenticationCode(for: Data([0x01]), using: symmetricKey))
+        let newChainKey = Data(HMAC<SHA256>.authenticationCode(for: Data([0x02]), using: symmetricKey))
+        return (newChainKey, messageKey)
+    }
+
+    // MARK: - Self-Encryption Key
+
+    /// Derive static AES-256 key from identity key for self-encrypted message copies.
+    /// Matches Python: derive_self_encryption_key(identity_private)
+    static func deriveSelfEncryptionKey(identityPrivateRaw: Data) -> Data {
+        hkdfDerive(
+            inputKey: identityPrivateRaw,
+            salt: Data(Constants.selfEncryptionSalt.utf8),
+            info: Data(Constants.selfEncryptionInfo.utf8),
+            length: 32
+        )
+    }
+
+    // MARK: - Local Storage Key
+
+    /// Derive AES-256 key for encrypting local session/sender key files.
+    /// Matches Python: derive_local_storage_key(identity_private)
+    static func deriveLocalStorageKey(identityPrivateRaw: Data) -> Data {
+        hkdfDerive(
+            inputKey: identityPrivateRaw,
+            salt: Data(Constants.localStorageSalt.utf8),
+            info: Data(Constants.localStorageInfo.utf8),
+            length: 32
+        )
+    }
+
+    // MARK: - Local File Encryption
+
+    /// Encrypt data for local storage. Format: nonce(12) + tag(16) + ciphertext
+    /// Matches Python: _encrypt_local(data, key)
+    static func encryptLocal(_ data: Data, key: Data) throws -> Data {
+        let symmetricKey = SymmetricKey(data: key)
+        let sealedBox = try AES.GCM.seal(data, using: symmetricKey)
+
+        var result = Data()
+        result.append(Data(sealedBox.nonce))       // 12 bytes
+        result.append(Data(sealedBox.tag))          // 16 bytes
+        result.append(Data(sealedBox.ciphertext))   // N bytes
+        return result
+    }
+
+    /// Decrypt locally stored data. Format: nonce(12) + tag(16) + ciphertext
+    /// Matches Python: _decrypt_local(raw, key)
+    static func decryptLocal(_ raw: Data, key: Data) throws -> Data {
+        guard raw.count >= 28 else {  // 12 + 16 minimum
+            throw CryptoError.decryptionFailed("Local encrypted data too short")
+        }
+
+        let nonce = raw[0..<12]
+        let tag = raw[12..<28]
+        let ct = raw[28...]
+
+        let symmetricKey = SymmetricKey(data: key)
+        let gcmNonce = try AES.GCM.Nonce(data: nonce)
+
+        let sealedBox = try AES.GCM.SealedBox(
+            nonce: gcmNonce,
+            ciphertext: ct,
+            tag: tag
+        )
+
+        do {
+            return try AES.GCM.open(sealedBox, using: symmetricKey)
+        } catch {
+            throw CryptoError.decryptionFailed("Local storage decryption failed")
+        }
+    }
+}
--- a/ios_client/EncryptedChat/Crypto/DoubleRatchet.swift
+++ b/ios_client/EncryptedChat/Crypto/DoubleRatchet.swift
@@ -0,0 +1,371 @@
+import Foundation
+import CryptoKit
+
+/// Ratchet header sent with each message
+struct RatchetHeader {
+    let dhPub: Data   // sender's current ratchet public key (32 bytes)
+    let n: Int        // message number in current sending chain
+    let pn: Int       // number of messages in previous sending chain
+
+    /// Serialize header to JSON bytes for use as AAD.
+    /// Matches Python: RatchetHeader.serialize()
+    func serialize() -> Data {
+        let dict: [String: Any] = [
+            "dh_pub": dhPub.hexString,
+            "n": n,
+            "pn": pn,
+        ]
+        // Must produce consistent JSON — sorted keys for determinism
+        return try! JSONSerialization.data(withJSONObject: dict, options: .sortedKeys)
+    }
+
+    /// Convert to dictionary for protocol.
+    /// Matches Python: RatchetHeader.to_dict()
+    func toDict() -> [String: Any] {
+        [
+            "dh_pub": dhPub.hexString,
+            "n": n,
+            "pn": pn,
+        ]
+    }
+
+    /// Parse from dictionary.
+    /// Matches Python: RatchetHeader.from_dict(d)
+    static func fromDict(_ d: [String: Any]) throws -> RatchetHeader {
+        guard let dhPubHex = d["dh_pub"] as? String,
+              let dhPub = Data(hexString: dhPubHex),
+              let n = d["n"] as? Int,
+              let pn = d["pn"] as? Int else {
+            throw CryptoError.invalidHeader("Missing or invalid header fields")
+        }
+        return RatchetHeader(dhPub: dhPub, n: n, pn: pn)
+    }
+}
+
+/// Signal Double Ratchet implementation.
+/// Matches Python: DoubleRatchet class in crypto_utils.py
+class DoubleRatchet {
+
+    private(set) var dhPair: (privateKey: Curve25519.KeyAgreement.PrivateKey,
+                               publicKey: Curve25519.KeyAgreement.PublicKey)?
+    private(set) var dhRemote: Curve25519.KeyAgreement.PublicKey?
+    private(set) var rootKey: Data = Data()
+    private(set) var sendChainKey: Data?
+    private(set) var recvChainKey: Data?
+    private(set) var sendN: Int = 0
+    private(set) var recvN: Int = 0
+    private(set) var prevSendN: Int = 0
+    // Skipped message keys: "dh_pub_hex:n" → message_key
+    private(set) var skipped: [String: Data] = [:]
+
+    /// Attached X3DH header — set when creating a new session, consumed on first send.
+    /// Matches Python: ratchet._x3dh_header
+    var x3dhHeader: [String: Any]?
+
+    init() {}
+
+    // MARK: - Initialization
+
+    /// Initialize as initiator (Alice) after X3DH.
+    /// Matches Python: DoubleRatchet.init_alice(shared_secret, bob_spk_pub)
+    static func initAlice(sharedSecret: Data, bobSpkPub: Curve25519.KeyAgreement.PublicKey) throws -> DoubleRatchet {
+        let ratchet = DoubleRatchet()
+        let (priv, pub) = X25519Crypto.generateKeypair()
+        ratchet.dhPair = (priv, pub)
+        ratchet.dhRemote = bobSpkPub
+
+        // Perform DH ratchet to derive send chain
+        let dhOutput = try X25519Crypto.dh(priv, bobSpkPub)
+        let (newRK, sendCK) = CryptoUtils.kdfRK(rootKey: sharedSecret, dhOutput: dhOutput)
+        ratchet.rootKey = newRK
+        ratchet.sendChainKey = sendCK
+        ratchet.recvChainKey = nil
+        ratchet.sendN = 0
+        ratchet.recvN = 0
+        ratchet.prevSendN = 0
+        return ratchet
+    }
+
+    /// Initialize as responder (Bob) after X3DH.
+    /// Matches Python: DoubleRatchet.init_bob(shared_secret, spk_pair)
+    static func initBob(
+        sharedSecret: Data,
+        spkPair: (privateKey: Curve25519.KeyAgreement.PrivateKey, publicKey: Curve25519.KeyAgreement.PublicKey)
+    ) -> DoubleRatchet {
+        let ratchet = DoubleRatchet()
+        ratchet.dhPair = spkPair
+        ratchet.rootKey = sharedSecret
+        ratchet.sendChainKey = nil
+        ratchet.recvChainKey = nil
+        ratchet.sendN = 0
+        ratchet.recvN = 0
+        ratchet.prevSendN = 0
+        return ratchet
+    }
+
+    // MARK: - Encrypt
+
+    /// Encrypt a message.
+    /// Returns (header dict, ciphertext with tag, nonce).
+    /// Matches Python: DoubleRatchet.encrypt(plaintext)
+    func encrypt(_ plaintext: Data) throws -> (header: [String: Any], ciphertext: Data, nonce: Data) {
+        guard sendChainKey != nil else {
+            throw CryptoError.ratchetError("Send chain not initialized")
+        }
+        guard let dhPair = dhPair else {
+            throw CryptoError.ratchetError("DH pair not set")
+        }
+
+        let (newCK, messageKey) = CryptoUtils.kdfCK(chainKey: sendChainKey!)
+        sendChainKey = newCK
+
+        let header = RatchetHeader(
+            dhPub: X25519Crypto.serializePublic(dhPair.publicKey),
+            n: sendN,
+            pn: prevSendN
+        )
+
+        let nonce = Data.randomBytes(12)
+        let aad = header.serialize()
+        let ctWithTag = try CryptoUtils.aesGcmEncrypt(plaintext, key: messageKey, nonce: nonce, aad: aad)
+
+        sendN += 1
+
+        return (header.toDict(), ctWithTag, nonce)
+    }
+
+    // MARK: - Decrypt
+
+    /// Decrypt a message. Handles DH ratchet step if new dh_pub.
+    /// State is snapshotted before modification and restored on failure (M9 fix).
+    /// Matches Python: DoubleRatchet.decrypt(header_dict, ciphertext, nonce)
+    func decrypt(headerDict: [String: Any], ciphertext: Data, nonce: Data) throws -> Data {
+        let header = try RatchetHeader.fromDict(headerDict)
+        let remoteDhPubBytes = header.dhPub
+
+        // Check if this is from a skipped message
+        let skipKey = "\(remoteDhPubBytes.hexString):\(header.n)"
+        if let mk = skipped[skipKey] {
+            skipped.removeValue(forKey: skipKey)
+            let aad = header.serialize()
+            do {
+                return try CryptoUtils.aesGcmDecrypt(ciphertext, key: mk, nonce: nonce, aad: aad)
+            } catch {
+                // Restore skipped key on failure
+                skipped[skipKey] = mk
+                throw error
+            }
+        }
+
+        // Snapshot state before modifications
+        let snap = snapshot()
+
+        do {
+            let remoteDhPub = try X25519Crypto.loadPublic(remoteDhPubBytes)
+            let currentRemoteBytes: Data? = dhRemote.map { X25519Crypto.serializePublic($0) }
+
+            if currentRemoteBytes == nil || remoteDhPubBytes != currentRemoteBytes {
+                // New DH ratchet step
+                try skipMessages(until: header.pn)
+                try dhRatchet(remoteDhPub: remoteDhPub)
+            }
+
+            try skipMessages(until: header.n)
+
+            // Derive message key from receive chain
+            guard recvChainKey != nil else {
+                throw CryptoError.ratchetError("Receive chain key is nil")
+            }
+            let (newCK, mk) = CryptoUtils.kdfCK(chainKey: recvChainKey!)
+            recvChainKey = newCK
+            recvN += 1
+
+            let aad = header.serialize()
+            return try CryptoUtils.aesGcmDecrypt(ciphertext, key: mk, nonce: nonce, aad: aad)
+        } catch {
+            restore(snap)
+            throw error
+        }
+    }
+
+    // MARK: - State Snapshot/Restore (M9)
+
+    private struct Snapshot {
+        let dhPairPriv: Data?
+        let dhPairPub: Data?
+        let dhRemote: Data?
+        let rootKey: Data
+        let sendChainKey: Data?
+        let recvChainKey: Data?
+        let sendN: Int
+        let recvN: Int
+        let prevSendN: Int
+        let skipped: [String: Data]
+    }
+
+    private func snapshot() -> Snapshot {
+        Snapshot(
+            dhPairPriv: dhPair.map { X25519Crypto.serializePrivate($0.privateKey) },
+            dhPairPub: dhPair.map { X25519Crypto.serializePublic($0.publicKey) },
+            dhRemote: dhRemote.map { X25519Crypto.serializePublic($0) },
+            rootKey: rootKey,
+            sendChainKey: sendChainKey,
+            recvChainKey: recvChainKey,
+            sendN: sendN,
+            recvN: recvN,
+            prevSendN: prevSendN,
+            skipped: skipped
+        )
+    }
+
+    private func restore(_ snap: Snapshot) {
+        if let privData = snap.dhPairPriv, let pubData = snap.dhPairPub,
+           let priv = try? X25519Crypto.loadPrivate(privData),
+           let pub = try? X25519Crypto.loadPublic(pubData) {
+            dhPair = (priv, pub)
+        } else {
+            dhPair = nil
+        }
+        if let remoteData = snap.dhRemote, let remote = try? X25519Crypto.loadPublic(remoteData) {
+            dhRemote = remote
+        } else {
+            dhRemote = nil
+        }
+        rootKey = snap.rootKey
+        sendChainKey = snap.sendChainKey
+        recvChainKey = snap.recvChainKey
+        sendN = snap.sendN
+        recvN = snap.recvN
+        prevSendN = snap.prevSendN
+        skipped = snap.skipped
+    }
+
+    // MARK: - Internal Ratchet Operations
+
+    private func skipMessages(until: Int) throws {
+        guard recvChainKey != nil else { return }
+        if until - recvN > Constants.maxSkip {
+            throw CryptoError.maxSkipExceeded
+        }
+        while recvN < until {
+            let (newCK, mk) = CryptoUtils.kdfCK(chainKey: recvChainKey!)
+            recvChainKey = newCK
+            let remoteHex = dhRemote.map { X25519Crypto.serializePublic($0).hexString } ?? ""
+            skipped["\(remoteHex):\(recvN)"] = mk
+            recvN += 1
+        }
+    }
+
+    private func dhRatchet(remoteDhPub: Curve25519.KeyAgreement.PublicKey) throws {
+        prevSendN = sendN
+        sendN = 0
+        recvN = 0
+        dhRemote = remoteDhPub
+
+        // Derive new receive chain key
+        guard let dhPair = dhPair else {
+            throw CryptoError.ratchetError("DH pair not set")
+        }
+        let dhOutput1 = try X25519Crypto.dh(dhPair.privateKey, remoteDhPub)
+        let (newRK1, recvCK) = CryptoUtils.kdfRK(rootKey: rootKey, dhOutput: dhOutput1)
+        rootKey = newRK1
+        recvChainKey = recvCK
+
+        // Generate new DH pair and derive new send chain key
+        let (newPriv, newPub) = X25519Crypto.generateKeypair()
+        self.dhPair = (newPriv, newPub)
+        let dhOutput2 = try X25519Crypto.dh(newPriv, remoteDhPub)
+        let (newRK2, sendCK) = CryptoUtils.kdfRK(rootKey: rootKey, dhOutput: dhOutput2)
+        rootKey = newRK2
+        sendChainKey = sendCK
+    }
+
+    // MARK: - State Export/Import
+
+    /// Serialize full ratchet state for persistent storage.
+    /// Produces JSON matching Python's DoubleRatchet.export_state() exactly.
+    func exportState() throws -> Data {
+        var state: [String: Any] = [:]
+
+        if let pair = dhPair {
+            state["dh_priv"] = X25519Crypto.serializePrivate(pair.privateKey).hexString
+            state["dh_pub"] = X25519Crypto.serializePublic(pair.publicKey).hexString
+        } else {
+            state["dh_priv"] = NSNull()
+            state["dh_pub"] = NSNull()
+        }
+
+        if let remote = dhRemote {
+            state["dh_remote"] = X25519Crypto.serializePublic(remote).hexString
+        } else {
+            state["dh_remote"] = NSNull()
+        }
+
+        state["root_key"] = rootKey.hexString
+        state["send_ck"] = sendChainKey?.hexString ?? NSNull()
+        state["recv_ck"] = recvChainKey?.hexString ?? NSNull()
+        state["send_n"] = sendN
+        state["recv_n"] = recvN
+        state["prev_send_n"] = prevSendN
+
+        // Skipped keys: Python format is "dh_pub_hex:n" -> message_key_hex
+        var skippedDict: [String: String] = [:]
+        for (key, value) in skipped {
+            skippedDict[key] = value.hexString
+        }
+        state["skipped"] = skippedDict
+
+        return try JSONSerialization.data(withJSONObject: state)
+    }
+
+    /// Deserialize ratchet state.
+    /// Matches Python: DoubleRatchet.import_state(data)
+    static func importState(_ data: Data) throws -> DoubleRatchet {
+        guard let state = try JSONSerialization.jsonObject(with: data) as? [String: Any] else {
+            throw CryptoError.stateImportFailed("Invalid JSON")
+        }
+
+        let r = DoubleRatchet()
+
+        if let dhPrivHex = state["dh_priv"] as? String,
+           let dhPubHex = state["dh_pub"] as? String,
+           let privData = Data(hexString: dhPrivHex),
+           let pubData = Data(hexString: dhPubHex) {
+            let priv = try X25519Crypto.loadPrivate(privData)
+            let pub = try X25519Crypto.loadPublic(pubData)
+            r.dhPair = (priv, pub)
+        }
+
+        if let dhRemoteHex = state["dh_remote"] as? String,
+           let remoteData = Data(hexString: dhRemoteHex) {
+            r.dhRemote = try X25519Crypto.loadPublic(remoteData)
+        }
+
+        guard let rootKeyHex = state["root_key"] as? String,
+              let rootKey = Data(hexString: rootKeyHex) else {
+            throw CryptoError.stateImportFailed("Missing root_key")
+        }
+        r.rootKey = rootKey
+
+        if let sendCKHex = state["send_ck"] as? String, let ck = Data(hexString: sendCKHex) {
+            r.sendChainKey = ck
+        }
+        if let recvCKHex = state["recv_ck"] as? String, let ck = Data(hexString: recvCKHex) {
+            r.recvChainKey = ck
+        }
+
+        r.sendN = state["send_n"] as? Int ?? 0
+        r.recvN = state["recv_n"] as? Int ?? 0
+        r.prevSendN = state["prev_send_n"] as? Int ?? 0
+
+        if let skippedDict = state["skipped"] as? [String: String] {
+            for (key, valueHex) in skippedDict {
+                if let value = Data(hexString: valueHex) {
+                    r.skipped[key] = value
+                }
+            }
+        }
+
+        return r
+    }
+}
--- a/ios_client/EncryptedChat/Crypto/Ed25519Crypto.swift
+++ b/ios_client/EncryptedChat/Crypto/Ed25519Crypto.swift
@@ -0,0 +1,73 @@
+import Foundation
+import CryptoKit
+
+/// Ed25519 signing operations — Identity Key management
+enum Ed25519Crypto {
+
+    // MARK: - Key Generation
+
+    /// Generate Ed25519 keypair
+    static func generateKeypair() -> (privateKey: Curve25519.Signing.PrivateKey, publicKey: Curve25519.Signing.PublicKey) {
+        let privateKey = Curve25519.Signing.PrivateKey()
+        return (privateKey, privateKey.publicKey)
+    }
+
+    // MARK: - Serialization
+
+    /// Serialize Ed25519 private key. With password: raw 32B → ECP1. Without: raw 32B.
+    /// Matches Python: serialize_ed25519_private(key, password=None)
+    static func serializePrivate(_ key: Curve25519.Signing.PrivateKey, password: Data? = nil) throws -> Data {
+        let raw = key.rawData  // 32 bytes
+        if let password = password {
+            return try KeyEncryption.encrypt(raw, password: password)
+        }
+        return raw
+    }
+
+    /// Serialize Ed25519 public key to 32 raw bytes.
+    /// Matches Python: serialize_ed25519_public(key)
+    static func serializePublic(_ key: Curve25519.Signing.PublicKey) -> Data {
+        key.rawData  // 32 bytes
+    }
+
+    // MARK: - Loading
+
+    /// Load Ed25519 private key. Auto-detects ECP1 / raw 32B.
+    /// Matches Python: load_ed25519_private(data, password=None)
+    static func loadPrivate(_ data: Data, password: Data? = nil) throws -> Curve25519.Signing.PrivateKey {
+        if KeyEncryption.isECP1Format(data) {
+            guard let pwd = password else {
+                throw CryptoError.invalidKeyData("ECP1 key requires password")
+            }
+            let raw = try KeyEncryption.decrypt(data, password: pwd)
+            return try Curve25519.Signing.PrivateKey(rawRepresentation: raw)
+        }
+        if data.count == 32 {
+            return try Curve25519.Signing.PrivateKey(rawRepresentation: data)
+        }
+        throw CryptoError.invalidKeyData("Cannot parse Ed25519 private key (\(data.count) bytes)")
+    }
+
+    /// Load Ed25519 public key from 32 raw bytes.
+    /// Matches Python: load_ed25519_public(data)
+    static func loadPublic(_ data: Data) throws -> Curve25519.Signing.PublicKey {
+        guard data.count == 32 else {
+            throw CryptoError.invalidKeyData("Ed25519 public key must be 32 bytes, got \(data.count)")
+        }
+        return try Curve25519.Signing.PublicKey(rawRepresentation: data)
+    }
+
+    // MARK: - Sign / Verify
+
+    /// Sign data with Ed25519. Returns 64-byte signature.
+    /// Matches Python: ed25519_sign(private_key, data)
+    static func sign(_ privateKey: Curve25519.Signing.PrivateKey, data: Data) throws -> Data {
+        Data(try privateKey.signature(for: data))
+    }
+
+    /// Verify Ed25519 signature.
+    /// Matches Python: ed25519_verify(public_key, signature, data)
+    static func verify(_ publicKey: Curve25519.Signing.PublicKey, signature: Data, data: Data) -> Bool {
+        publicKey.isValidSignature(signature, for: data)
+    }
+}
--- a/ios_client/EncryptedChat/Crypto/FieldArithmetic.swift
+++ b/ios_client/EncryptedChat/Crypto/FieldArithmetic.swift
@@ -0,0 +1,231 @@
+import Foundation
+
+/// Pure Swift GF(2^255-19) arithmetic for Ed25519 → X25519 public key conversion.
+///
+/// The conversion formula is: u = (1 + y) / (1 - y) mod p
+/// where p = 2^255 - 19, and y is the Ed25519 public key's y-coordinate.
+///
+/// Uses 4-limb UInt64 representation (little-endian).
+enum FieldArithmetic {
+
+    // p = 2^255 - 19
+    static let p: [UInt64] = [
+        0xFFFF_FFFF_FFFF_FFED,  // limb 0 (least significant)
+        0xFFFF_FFFF_FFFF_FFFF,  // limb 1
+        0xFFFF_FFFF_FFFF_FFFF,  // limb 2
+        0x7FFF_FFFF_FFFF_FFFF,  // limb 3 (most significant, 2^63 - 1 accounting for -19)
+    ]
+
+    /// Load a 256-bit little-endian byte array into 4 UInt64 limbs
+    static func load(_ bytes: Data) -> [UInt64] {
+        precondition(bytes.count == 32)
+        var limbs = [UInt64](repeating: 0, count: 4)
+        for i in 0..<4 {
+            var val: UInt64 = 0
+            for j in 0..<8 {
+                val |= UInt64(bytes[i * 8 + j]) << (j * 8)
+            }
+            limbs[i] = val
+        }
+        return limbs
+    }
+
+    /// Store 4 UInt64 limbs as 32 little-endian bytes
+    static func store(_ limbs: [UInt64]) -> Data {
+        var bytes = Data(count: 32)
+        for i in 0..<4 {
+            for j in 0..<8 {
+                bytes[i * 8 + j] = UInt8((limbs[i] >> (j * 8)) & 0xFF)
+            }
+        }
+        return bytes
+    }
+
+    /// a + b mod p
+    static func add(_ a: [UInt64], _ b: [UInt64]) -> [UInt64] {
+        var result = [UInt64](repeating: 0, count: 4)
+        var carry: UInt64 = 0
+        for i in 0..<4 {
+            let (sum1, c1) = a[i].addingReportingOverflow(b[i])
+            let (sum2, c2) = sum1.addingReportingOverflow(carry)
+            result[i] = sum2
+            carry = (c1 ? 1 : 0) + (c2 ? 1 : 0)
+        }
+        // Reduce mod p
+        return reduceOnce(result, carry: carry)
+    }
+
+    /// a - b mod p
+    static func sub(_ a: [UInt64], _ b: [UInt64]) -> [UInt64] {
+        var result = [UInt64](repeating: 0, count: 4)
+        var borrow: UInt64 = 0
+        for i in 0..<4 {
+            let (diff1, b1) = a[i].subtractingReportingOverflow(b[i])
+            let (diff2, b2) = diff1.subtractingReportingOverflow(borrow)
+            result[i] = diff2
+            borrow = (b1 ? 1 : 0) + (b2 ? 1 : 0)
+        }
+        if borrow > 0 {
+            // Add p back
+            var c: UInt64 = 0
+            for i in 0..<4 {
+                let (s1, c1) = result[i].addingReportingOverflow(p[i])
+                let (s2, c2) = s1.addingReportingOverflow(c)
+                result[i] = s2
+                c = (c1 ? 1 : 0) + (c2 ? 1 : 0)
+            }
+        }
+        return result
+    }
+
+    /// Multiply two 256-bit numbers mod p using schoolbook multiplication
+    static func mul(_ a: [UInt64], _ b: [UInt64]) -> [UInt64] {
+        // Full 512-bit product in 8 limbs
+        var product = [UInt64](repeating: 0, count: 8)
+
+        for i in 0..<4 {
+            var carry: UInt64 = 0
+            for j in 0..<4 {
+                let (hi, lo) = a[i].multipliedFullWidth(by: b[j])
+                let (sum1, c1) = product[i + j].addingReportingOverflow(lo)
+                let (sum2, c2) = sum1.addingReportingOverflow(carry)
+                product[i + j] = sum2
+                carry = hi + (c1 ? 1 : 0) + (c2 ? 1 : 0)
+            }
+            product[i + 4] = carry
+        }
+
+        // Reduce mod p using Barrett-like reduction
+        // Since p = 2^255 - 19, for a 512-bit number we can use:
+        // x mod p = (x_low + x_high * 2^256) mod p
+        // Since 2^255 ≡ 19 (mod p), 2^256 ≡ 38 (mod p)
+        return reduceFull(product)
+    }
+
+    /// Reduce 512-bit product mod p using 2^256 ≡ 38 (mod p)
+    private static func reduceFull(_ product: [UInt64]) -> [UInt64] {
+        // Split: low = product[0..3], high = product[4..7]
+        // result = low + high * 38
+        var result = [UInt64](repeating: 0, count: 5)
+
+        // Start with low part
+        for i in 0..<4 {
+            result[i] = product[i]
+        }
+
+        // Add high * 38
+        var carry: UInt64 = 0
+        for i in 0..<4 {
+            let (hi, lo) = product[i + 4].multipliedFullWidth(by: 38)
+            let (sum1, c1) = result[i].addingReportingOverflow(lo)
+            let (sum2, c2) = sum1.addingReportingOverflow(carry)
+            result[i] = sum2
+            carry = hi + (c1 ? 1 : 0) + (c2 ? 1 : 0)
+        }
+        result[4] = carry
+
+        // The result might still be >= p, so reduce once more
+        // result[4] * 2^256 ≡ result[4] * 38 (mod p)
+        var extra: UInt64 = result[4]
+        result[4] = 0
+        if extra > 0 {
+            let (hi, lo) = extra.multipliedFullWidth(by: 38)
+            let (sum1, c1) = result[0].addingReportingOverflow(lo)
+            result[0] = sum1
+            var c = hi + (c1 ? 1 : 0)
+            for i in 1..<4 {
+                let (s, cf) = result[i].addingReportingOverflow(c)
+                result[i] = s
+                c = cf ? 1 : 0
+            }
+            // One more round if carry
+            if c > 0 {
+                let (s, _) = result[0].addingReportingOverflow(c * 38)
+                result[0] = s
+            }
+        }
+
+        var out = Array(result[0..<4])
+        // Final reduction: if >= p, subtract p
+        out = reduceOnce(out, carry: 0)
+        return out
+    }
+
+    /// If the number >= p, subtract p
+    private static func reduceOnce(_ val: [UInt64], carry: UInt64) -> [UInt64] {
+        if carry > 0 || isGreaterOrEqual(val, p) {
+            var result = [UInt64](repeating: 0, count: 4)
+            var borrow: UInt64 = 0
+            for i in 0..<4 {
+                let (diff1, b1) = val[i].subtractingReportingOverflow(p[i])
+                let (diff2, b2) = diff1.subtractingReportingOverflow(borrow)
+                result[i] = diff2
+                borrow = (b1 ? 1 : 0) + (b2 ? 1 : 0)
+            }
+            // If borrow after subtracting p, the original was fine (shouldn't happen with carry)
+            if borrow > 0 && carry == 0 {
+                return val
+            }
+            return result
+        }
+        return val
+    }
+
+    /// Compare a >= b
+    private static func isGreaterOrEqual(_ a: [UInt64], _ b: [UInt64]) -> Bool {
+        for i in stride(from: 3, through: 0, by: -1) {
+            if a[i] > b[i] { return true }
+            if a[i] < b[i] { return false }
+        }
+        return true  // equal
+    }
+
+    /// Modular inverse using Fermat's little theorem: a^(-1) = a^(p-2) mod p
+    static func inverse(_ a: [UInt64]) -> [UInt64] {
+        // p - 2 = 2^255 - 21
+        let pMinus2 = sub(p, [2, 0, 0, 0])
+        return power(a, pMinus2)
+    }
+
+    /// Modular exponentiation using square-and-multiply
+    static func power(_ base: [UInt64], _ exp: [UInt64]) -> [UInt64] {
+        var result: [UInt64] = [1, 0, 0, 0]  // 1
+        var b = base
+
+        for i in 0..<4 {
+            var limb = exp[i]
+            let bits = (i == 3) ? 63 : 64  // top limb has 63 bits for p-2
+            for _ in 0..<bits {
+                if limb & 1 == 1 {
+                    result = mul(result, b)
+                }
+                b = mul(b, b)
+                limb >>= 1
+            }
+        }
+        return result
+    }
+
+    // MARK: - Ed25519 → X25519 Public Key Conversion
+
+    /// Convert Ed25519 public key (32 bytes) to X25519 public key (32 bytes).
+    /// Formula: u = (1 + y) * inverse(1 - y) mod p
+    static func ed25519PublicToX25519(_ ed25519Pub: Data) -> Data {
+        precondition(ed25519Pub.count == 32)
+
+        // Ed25519 public key is the y-coordinate with sign bit in the top bit of byte 31
+        var keyBytes = ed25519Pub
+        // Clear the sign bit
+        keyBytes[31] &= 0x7F
+
+        let y = load(keyBytes)
+        let one: [UInt64] = [1, 0, 0, 0]
+
+        let onePlusY = add(one, y)
+        let oneMinusY = sub(one, y)
+        let inv = inverse(oneMinusY)
+        let u = mul(onePlusY, inv)
+
+        return store(u)
+    }
+}
--- a/ios_client/EncryptedChat/Crypto/KeyEncryption.swift
+++ b/ios_client/EncryptedChat/Crypto/KeyEncryption.swift
@@ -0,0 +1,106 @@
+import Foundation
+import CryptoKit
+import CommonCrypto
+
+/// ECP1 key encryption format: PBKDF2-HMAC-SHA256 (600k iterations) + AES-256-GCM
+/// Wire format: magic(4) + salt(16) + nonce(12) + ciphertext_with_tag(N+16)
+enum KeyEncryption {
+
+    /// Encrypt raw key bytes with password using ECP1 format
+    static func encrypt(_ rawBytes: Data, password: Data) throws -> Data {
+        let salt = Data.randomBytes(16)
+        let derivedKey = try pbkdf2(password: password, salt: salt)
+
+        let nonce = Data.randomBytes(12)
+        let symmetricKey = SymmetricKey(data: derivedKey)
+        let gcmNonce = try AES.GCM.Nonce(data: nonce)
+
+        // AAD = ECP1 magic bytes (matching Python)
+        let sealedBox = try AES.GCM.seal(
+            rawBytes,
+            using: symmetricKey,
+            nonce: gcmNonce,
+            authenticating: Constants.ecp1Magic
+        )
+
+        // ciphertext + tag concatenated (matches Python's AESGCM.encrypt output)
+        var result = Data()
+        result.append(Constants.ecp1Magic)    // 4 bytes
+        result.append(salt)                    // 16 bytes
+        result.append(nonce)                   // 12 bytes
+        result.append(sealedBox.ciphertext)    // N bytes
+        result.append(sealedBox.tag)           // 16 bytes
+        return result
+    }
+
+    /// Decrypt ECP1-encrypted key bytes with password
+    static func decrypt(_ data: Data, password: Data) throws -> Data {
+        guard data.count >= 48 else {  // 4 + 16 + 12 + 16 minimum
+            throw CryptoError.invalidECP1Format
+        }
+        guard data.prefix(4) == Constants.ecp1Magic else {
+            throw CryptoError.invalidECP1Format
+        }
+
+        let salt = data[4..<20]
+        let nonce = data[20..<32]
+        let ctWithTag = data[32...]
+
+        guard ctWithTag.count >= 16 else {
+            throw CryptoError.invalidECP1Format
+        }
+
+        let derivedKey = try pbkdf2(password: password, salt: Data(salt))
+        let symmetricKey = SymmetricKey(data: derivedKey)
+        let gcmNonce = try AES.GCM.Nonce(data: nonce)
+
+        // Split ciphertext and tag
+        let ct = ctWithTag.prefix(ctWithTag.count - 16)
+        let tag = ctWithTag.suffix(16)
+
+        let sealedBox = try AES.GCM.SealedBox(
+            nonce: gcmNonce,
+            ciphertext: ct,
+            tag: tag
+        )
+
+        do {
+            return try AES.GCM.open(sealedBox, using: symmetricKey, authenticating: Constants.ecp1Magic)
+        } catch {
+            throw CryptoError.decryptionFailed("ECP1 decryption failed - wrong password?")
+        }
+    }
+
+    /// Check if data starts with ECP1 magic
+    static func isECP1Format(_ data: Data) -> Bool {
+        data.count >= 4 && data.prefix(4) == Constants.ecp1Magic
+    }
+
+    // MARK: - PBKDF2
+
+    /// Derive 32-byte key using PBKDF2-HMAC-SHA256 with 600k iterations
+    static func pbkdf2(password: Data, salt: Data) throws -> Data {
+        var derivedKey = Data(count: 32)
+        let status = derivedKey.withUnsafeMutableBytes { derivedKeyPtr in
+            password.withUnsafeBytes { passwordPtr in
+                salt.withUnsafeBytes { saltPtr in
+                    CCKeyDerivationPBKDF(
+                        CCPBKDFAlgorithm(kCCPBKDF2),
+                        passwordPtr.baseAddress?.assumingMemoryBound(to: Int8.self),
+                        password.count,
+                        saltPtr.baseAddress?.assumingMemoryBound(to: UInt8.self),
+                        salt.count,
+                        CCPseudoRandomAlgorithm(kCCPRFHmacAlgSHA256),
+                        Constants.pbkdf2Iterations,
+                        derivedKeyPtr.baseAddress?.assumingMemoryBound(to: UInt8.self),
+                        32
+                    )
+                }
+            }
+        }
+        guard status == kCCSuccess else {
+            throw CryptoError.pbkdf2Failed
+        }
+        return derivedKey
+    }
+}
--- a/ios_client/EncryptedChat/Crypto/RSACrypto.swift
+++ b/ios_client/EncryptedChat/Crypto/RSACrypto.swift
@@ -0,0 +1,309 @@
+import Foundation
+import Security
+
+/// RSA-4096 operations — used for login challenge-response ONLY
+enum RSACrypto {
+
+    // MARK: - Key Generation
+
+    /// Generate RSA-4096 keypair
+    static func generateKeypair() throws -> (privateKey: SecKey, publicKey: SecKey) {
+        let attributes: [String: Any] = [
+            kSecAttrKeyType as String: kSecAttrKeyTypeRSA,
+            kSecAttrKeySizeInBits as String: 4096,
+        ]
+
+        var error: Unmanaged<CFError>?
+        guard let privateKey = SecKeyCreateRandomKey(attributes as CFDictionary, &error) else {
+            throw CryptoError.rsaKeyGenerationFailed
+        }
+        guard let publicKey = SecKeyCopyPublicKey(privateKey) else {
+            throw CryptoError.rsaKeyGenerationFailed
+        }
+        return (privateKey, publicKey)
+    }
+
+    // MARK: - Serialization
+
+    /// Serialize RSA private key. With password: DER → ECP1. Without: PEM PKCS#8.
+    static func serializePrivateKey(_ key: SecKey, password: Data? = nil) throws -> Data {
+        var error: Unmanaged<CFError>?
+        guard let derData = SecKeyCopyExternalRepresentation(key, &error) as Data? else {
+            throw CryptoError.rsaOperationFailed("Failed to export private key")
+        }
+
+        // SecKey exports in PKCS#1 format on iOS — wrap in PKCS#8 for Python compat
+        let pkcs8 = wrapRSAPrivateKeyPKCS8(derData)
+
+        if let password = password {
+            return try KeyEncryption.encrypt(pkcs8, password: password)
+        }
+
+        // PEM encode for Python compatibility
+        return pemEncode(pkcs8, label: "PRIVATE KEY")
+    }
+
+    /// Serialize RSA public key as PEM SubjectPublicKeyInfo (Python-compatible)
+    static func serializePublicKey(_ key: SecKey) throws -> Data {
+        var error: Unmanaged<CFError>?
+        guard let derData = SecKeyCopyExternalRepresentation(key, &error) as Data? else {
+            throw CryptoError.rsaOperationFailed("Failed to export public key")
+        }
+
+        // SecKey exports PKCS#1 on iOS — wrap in SubjectPublicKeyInfo
+        let spki = wrapRSAPublicKeySPKI(derData)
+        return pemEncode(spki, label: "PUBLIC KEY")
+    }
+
+    /// Load RSA private key. Auto-detects ECP1 vs PEM format.
+    static func loadPrivateKey(_ data: Data, password: Data? = nil) throws -> SecKey {
+        let derData: Data
+
+        if KeyEncryption.isECP1Format(data) {
+            guard let pwd = password else {
+                throw CryptoError.invalidKeyData("ECP1 key requires password")
+            }
+            let raw = try KeyEncryption.decrypt(data, password: pwd)
+            derData = unwrapPKCS8ToRSAPrivateKey(raw)
+        } else {
+            // PEM format
+            let pem = String(data: data, encoding: .utf8) ?? ""
+            derData = try pemDecode(pem, label: "PRIVATE KEY")
+                .flatMap { unwrapPKCS8ToRSAPrivateKey($0) }
+                ?? pemDecode(pem, label: "RSA PRIVATE KEY")
+                ?? { throw CryptoError.invalidKeyData("Cannot parse RSA private key PEM") }()
+        }
+
+        let attributes: [String: Any] = [
+            kSecAttrKeyType as String: kSecAttrKeyTypeRSA,
+            kSecAttrKeyClass as String: kSecAttrKeyClassPrivate,
+        ]
+
+        var error: Unmanaged<CFError>?
+        guard let key = SecKeyCreateWithData(derData as CFData, attributes as CFDictionary, &error) else {
+            throw CryptoError.invalidKeyData("Failed to create RSA private key from DER")
+        }
+        return key
+    }
+
+    /// Load RSA public key from PEM
+    static func loadPublicKey(_ pemData: Data) throws -> SecKey {
+        let pem = String(data: pemData, encoding: .utf8) ?? ""
+
+        // Try SubjectPublicKeyInfo (PUBLIC KEY), unwrap to PKCS#1
+        let derData: Data
+        if let spki = pemDecode(pem, label: "PUBLIC KEY") {
+            derData = unwrapSPKIToRSAPublicKey(spki)
+        } else if let pkcs1 = pemDecode(pem, label: "RSA PUBLIC KEY") {
+            derData = pkcs1
+        } else {
+            throw CryptoError.invalidKeyData("Cannot parse RSA public key PEM")
+        }
+
+        let attributes: [String: Any] = [
+            kSecAttrKeyType as String: kSecAttrKeyTypeRSA,
+            kSecAttrKeyClass as String: kSecAttrKeyClassPublic,
+        ]
+
+        var error: Unmanaged<CFError>?
+        guard let key = SecKeyCreateWithData(derData as CFData, attributes as CFDictionary, &error) else {
+            throw CryptoError.invalidKeyData("Failed to create RSA public key from DER")
+        }
+        return key
+    }
+
+    // MARK: - Sign / Verify
+
+    /// Sign data with RSA-PSS SHA-256.
+    /// Note: iOS uses salt_length = hash_length (32). Server must use PSS.AUTO to verify.
+    static func sign(_ privateKey: SecKey, data: Data) throws -> Data {
+        var error: Unmanaged<CFError>?
+        guard let signature = SecKeyCreateSignature(
+            privateKey,
+            .rsaSignatureMessagePSSSHA256,
+            data as CFData,
+            &error
+        ) as Data? else {
+            throw CryptoError.rsaOperationFailed("RSA signing failed")
+        }
+        return signature
+    }
+
+    /// Verify RSA-PSS SHA-256 signature
+    static func verify(_ publicKey: SecKey, signature: Data, data: Data) -> Bool {
+        SecKeyVerifySignature(
+            publicKey,
+            .rsaSignatureMessagePSSSHA256,
+            data as CFData,
+            signature as CFData,
+            nil
+        )
+    }
+
+    // MARK: - PEM Helpers
+
+    private static func pemEncode(_ der: Data, label: String) -> Data {
+        let base64 = der.base64EncodedString(options: .lineLength64Characters)
+        let pem = "-----BEGIN \(label)-----\n\(base64)\n-----END \(label)-----\n"
+        return Data(pem.utf8)
+    }
+
+    private static func pemDecode(_ pem: String, label: String) -> Data? {
+        let beginMarker = "-----BEGIN \(label)-----"
+        let endMarker = "-----END \(label)-----"
+
+        guard let beginRange = pem.range(of: beginMarker),
+              let endRange = pem.range(of: endMarker) else {
+            return nil
+        }
+
+        let base64String = pem[beginRange.upperBound..<endRange.lowerBound]
+            .replacingOccurrences(of: "\n", with: "")
+            .replacingOccurrences(of: "\r", with: "")
+            .replacingOccurrences(of: " ", with: "")
+
+        return Data(base64Encoded: base64String)
+    }
+
+    // MARK: - ASN.1 PKCS#8 / SPKI Wrappers
+
+    // SecKey on iOS exports RSA keys in PKCS#1 format, but Python expects PKCS#8 / SPKI.
+    // These functions add/remove the ASN.1 wrapping.
+
+    // RSA OID: 1.2.840.113549.1.1.1
+    private static let rsaOID: [UInt8] = [0x06, 0x09, 0x2A, 0x86, 0x48, 0x86, 0xF7, 0x0D, 0x01, 0x01, 0x01]
+    private static let nullParam: [UInt8] = [0x05, 0x00]
+
+    /// Wrap PKCS#1 RSA private key in PKCS#8 PrivateKeyInfo envelope
+    private static func wrapRSAPrivateKeyPKCS8(_ pkcs1: Data) -> Data {
+        // PrivateKeyInfo ::= SEQUENCE {
+        //   version INTEGER (0),
+        //   algorithm AlgorithmIdentifier,
+        //   privateKey OCTET STRING (containing PKCS#1 key)
+        // }
+        let version = Data([0x02, 0x01, 0x00]) // INTEGER 0
+        let algorithmSeq = asn1Sequence(Data(rsaOID) + Data(nullParam))
+        let privateKeyOctet = asn1OctetString(pkcs1)
+        return asn1Sequence(version + algorithmSeq + privateKeyOctet)
+    }
+
+    /// Unwrap PKCS#8 to get PKCS#1 RSA private key
+    private static func unwrapPKCS8ToRSAPrivateKey(_ pkcs8: Data) -> Data {
+        // Parse SEQUENCE, skip version + algorithm, extract OCTET STRING
+        guard pkcs8.count > 2 else { return pkcs8 }
+
+        var offset = 0
+        // Outer SEQUENCE
+        guard pkcs8[offset] == 0x30 else { return pkcs8 }
+        offset += 1
+        offset = skipASN1Length(pkcs8, offset: offset)
+
+        // Version INTEGER
+        guard offset < pkcs8.count, pkcs8[offset] == 0x02 else { return pkcs8 }
+        offset += 1
+        let versionLen = readASN1Length(pkcs8, offset: &offset)
+        offset += versionLen
+
+        // Algorithm SEQUENCE
+        guard offset < pkcs8.count, pkcs8[offset] == 0x30 else { return pkcs8 }
+        offset += 1
+        let algoLen = readASN1Length(pkcs8, offset: &offset)
+        offset += algoLen
+
+        // Private key OCTET STRING
+        guard offset < pkcs8.count, pkcs8[offset] == 0x04 else { return pkcs8 }
+        offset += 1
+        let keyLen = readASN1Length(pkcs8, offset: &offset)
+        guard offset + keyLen <= pkcs8.count else { return pkcs8 }
+        return Data(pkcs8[offset..<(offset + keyLen)])
+    }
+
+    /// Wrap PKCS#1 RSA public key in SubjectPublicKeyInfo
+    private static func wrapRSAPublicKeySPKI(_ pkcs1: Data) -> Data {
+        // SubjectPublicKeyInfo ::= SEQUENCE {
+        //   algorithm AlgorithmIdentifier,
+        //   subjectPublicKey BIT STRING (containing PKCS#1 key)
+        // }
+        let algorithmSeq = asn1Sequence(Data(rsaOID) + Data(nullParam))
+        let bitString = asn1BitString(pkcs1)
+        return asn1Sequence(algorithmSeq + bitString)
+    }
+
+    /// Unwrap SubjectPublicKeyInfo to get PKCS#1 RSA public key
+    private static func unwrapSPKIToRSAPublicKey(_ spki: Data) -> Data {
+        guard spki.count > 2 else { return spki }
+
+        var offset = 0
+        // Outer SEQUENCE
+        guard spki[offset] == 0x30 else { return spki }
+        offset += 1
+        offset = skipASN1Length(spki, offset: offset)
+
+        // Algorithm SEQUENCE
+        guard offset < spki.count, spki[offset] == 0x30 else { return spki }
+        offset += 1
+        let algoLen = readASN1Length(spki, offset: &offset)
+        offset += algoLen
+
+        // BIT STRING
+        guard offset < spki.count, spki[offset] == 0x03 else { return spki }
+        offset += 1
+        let bitLen = readASN1Length(spki, offset: &offset)
+        // Skip the unused bits byte
+        guard offset < spki.count, spki[offset] == 0x00 else { return spki }
+        offset += 1
+        let keyLen = bitLen - 1
+        guard offset + keyLen <= spki.count else { return spki }
+        return Data(spki[offset..<(offset + keyLen)])
+    }
+
+    // MARK: - ASN.1 Primitives
+
+    private static func asn1Length(_ length: Int) -> Data {
+        if length < 0x80 {
+            return Data([UInt8(length)])
+        } else if length <= 0xFF {
+            return Data([0x81, UInt8(length)])
+        } else if length <= 0xFFFF {
+            return Data([0x82, UInt8(length >> 8), UInt8(length & 0xFF)])
+        } else {
+            return Data([0x83, UInt8(length >> 16), UInt8((length >> 8) & 0xFF), UInt8(length & 0xFF)])
+        }
+    }
+
+    private static func asn1Sequence(_ content: Data) -> Data {
+        Data([0x30]) + asn1Length(content.count) + content
+    }
+
+    private static func asn1OctetString(_ content: Data) -> Data {
+        Data([0x04]) + asn1Length(content.count) + content
+    }
+
+    private static func asn1BitString(_ content: Data) -> Data {
+        // BIT STRING: tag + length + unused_bits(0) + content
+        Data([0x03]) + asn1Length(content.count + 1) + Data([0x00]) + content
+    }
+
+    private static func readASN1Length(_ data: Data, offset: inout Int) -> Int {
+        guard offset < data.count else { return 0 }
+        let first = data[offset]
+        offset += 1
+        if first < 0x80 {
+            return Int(first)
+        }
+        let numBytes = Int(first & 0x7F)
+        var length = 0
+        for _ in 0..<numBytes {
+            guard offset < data.count else { return length }
+            length = (length << 8) | Int(data[offset])
+            offset += 1
+        }
+        return length
+    }
+
+    private static func skipASN1Length(_ data: Data, offset: Int) -> Int {
+        var off = offset
+        _ = readASN1Length(data, offset: &off)
+        return off
+    }
+}
--- a/ios_client/EncryptedChat/Crypto/SenderKeyState.swift
+++ b/ios_client/EncryptedChat/Crypto/SenderKeyState.swift
@@ -0,0 +1,175 @@
+import Foundation
+import CryptoKit
+
+/// Sender key chain for group messaging.
+/// Each sender in a group has their own chain. Others receive the initial key via pairwise ratchet.
+/// Matches Python: SenderKeyState class in crypto_utils.py
+class SenderKeyState {
+
+    let senderKey: Data
+    let chainId: Data
+    private(set) var chainKey: Data
+    private(set) var n: Int
+    private var knownKeys: [Int: Data]
+
+    /// Initialize with optional sender key (generates random 32B if nil).
+    /// Matches Python: SenderKeyState.__init__(sender_key=None)
+    init(senderKey: Data? = nil) {
+        let key = senderKey ?? Data.randomBytes(32)
+        self.senderKey = key
+        self.chainId = Data(SHA256.hash(data: key))
+        self.chainKey = CryptoUtils.hkdfDerive(
+            inputKey: key,
+            salt: Data(repeating: 0x00, count: 32),
+            info: Data(Constants.senderKeyChainInfo.utf8),
+            length: 32
+        )
+        self.n = 0
+        self.knownKeys = [:]
+    }
+
+    /// Private init for import
+    private init(senderKey: Data, chainId: Data, chainKey: Data, n: Int, knownKeys: [Int: Data]) {
+        self.senderKey = senderKey
+        self.chainId = chainId
+        self.chainKey = chainKey
+        self.n = n
+        self.knownKeys = knownKeys
+    }
+
+    // MARK: - Encrypt
+
+    /// Encrypt with current chain key.
+    /// Returns (chainId hex, n, ciphertext with tag, nonce).
+    /// Matches Python: SenderKeyState.encrypt(plaintext)
+    func encrypt(_ plaintext: Data) throws -> (chainIdHex: String, n: Int, ciphertext: Data, nonce: Data) {
+        let (newCK, messageKey) = CryptoUtils.kdfCK(chainKey: chainKey)
+        chainKey = newCK
+
+        let nonce = Data.randomBytes(12)
+        // AAD = chainId + bigEndian(UInt32(n))
+        let aad = chainId + UInt32(n).bigEndianData
+        let ctWithTag = try CryptoUtils.aesGcmEncrypt(plaintext, key: messageKey, nonce: nonce, aad: aad)
+
+        let result = (chainIdHex: chainId.hexString, n: n, ciphertext: ctWithTag, nonce: nonce)
+        n += 1
+        return result
+    }
+
+    // MARK: - Decrypt
+
+    /// Decrypt a group message. Fast-forwards the chain if needed.
+    /// State is snapshotted before modification and restored on failure.
+    /// Matches Python: SenderKeyState.decrypt(chain_id_hex, n, ciphertext, nonce)
+    func decrypt(chainIdHex: String, n: Int, ciphertext: Data, nonce: Data) throws -> Data {
+        guard let expectedChainId = Data(hexString: chainIdHex) else {
+            throw CryptoError.senderKeyError("Invalid chain ID hex")
+        }
+        guard expectedChainId == chainId else {
+            throw CryptoError.senderKeyError("Chain ID mismatch")
+        }
+
+        if n - self.n > Constants.maxSenderKeySkip {
+            throw CryptoError.senderKeyError("Sender key skip too large (\(n - self.n) > \(Constants.maxSenderKeySkip))")
+        }
+
+        // Snapshot before fast-forward
+        let snapChainKey = chainKey
+        let snapN = self.n
+        let snapKnown = knownKeys
+
+        do {
+            // Fast-forward the chain to reach message n
+            while self.n <= n {
+                let (newCK, mk) = CryptoUtils.kdfCK(chainKey: chainKey)
+                chainKey = newCK
+                knownKeys[self.n] = mk
+                self.n += 1
+            }
+
+            guard let mk = knownKeys.removeValue(forKey: n) else {
+                throw CryptoError.senderKeyError("Message key for n=\(n) not available")
+            }
+
+            let aad = chainId + UInt32(n).bigEndianData
+            return try CryptoUtils.aesGcmDecrypt(ciphertext, key: mk, nonce: nonce, aad: aad)
+        } catch {
+            // Restore state on failure
+            chainKey = snapChainKey
+            self.n = snapN
+            knownKeys = snapKnown
+            throw error
+        }
+    }
+
+    // MARK: - Key Export/Import
+
+    /// Export sender key for distribution to group members.
+    /// Matches Python: SenderKeyState.export_key()
+    func exportKey() -> Data {
+        let dict: [String: Any] = ["sender_key": senderKey.hexString]
+        return try! JSONSerialization.data(withJSONObject: dict)
+    }
+
+    /// Initialize a receiving SenderKeyState from an exported key.
+    /// Matches Python: SenderKeyState.from_key(exported_key)
+    static func fromKey(_ exportedKey: Data) throws -> SenderKeyState {
+        guard let dict = try JSONSerialization.jsonObject(with: exportedKey) as? [String: Any],
+              let senderKeyHex = dict["sender_key"] as? String,
+              let senderKey = Data(hexString: senderKeyHex) else {
+            throw CryptoError.stateImportFailed("Invalid sender key export")
+        }
+        return SenderKeyState(senderKey: senderKey)
+    }
+
+    // MARK: - Full State Export/Import
+
+    /// Serialize full state for persistent storage.
+    /// Matches Python: SenderKeyState.export_state()
+    func exportState() -> Data {
+        var knownKeysDict: [String: String] = [:]
+        for (k, v) in knownKeys {
+            knownKeysDict[String(k)] = v.hexString
+        }
+        let state: [String: Any] = [
+            "sender_key": senderKey.hexString,
+            "chain_id": chainId.hexString,
+            "chain_key": chainKey.hexString,
+            "n": n,
+            "known_keys": knownKeysDict,
+        ]
+        return try! JSONSerialization.data(withJSONObject: state)
+    }
+
+    /// Deserialize full state.
+    /// Matches Python: SenderKeyState.import_state(data)
+    static func importState(_ data: Data) throws -> SenderKeyState {
+        guard let state = try JSONSerialization.jsonObject(with: data) as? [String: Any],
+              let senderKeyHex = state["sender_key"] as? String,
+              let senderKey = Data(hexString: senderKeyHex),
+              let chainIdHex = state["chain_id"] as? String,
+              let chainId = Data(hexString: chainIdHex),
+              let chainKeyHex = state["chain_key"] as? String,
+              let chainKey = Data(hexString: chainKeyHex),
+              let n = state["n"] as? Int else {
+            throw CryptoError.stateImportFailed("Invalid sender key state")
+        }
+
+        var knownKeys: [Int: Data] = [:]
+        if let knownKeysDict = state["known_keys"] as? [String: String] {
+            for (k, v) in knownKeysDict {
+                if let idx = Int(k), let data = Data(hexString: v) {
+                    knownKeys[idx] = data
+                }
+            }
+        }
+
+        return SenderKeyState(
+            senderKey: senderKey,
+            chainId: chainId,
+            chainKey: chainKey,
+            n: n,
+            knownKeys: knownKeys
+        )
+    }
+}
--- a/ios_client/EncryptedChat/Crypto/X25519Crypto.swift
+++ b/ios_client/EncryptedChat/Crypto/X25519Crypto.swift
@@ -0,0 +1,77 @@
+import Foundation
+import CryptoKit
+
+/// X25519 Diffie-Hellman key agreement
+enum X25519Crypto {
+
+    // MARK: - Key Generation
+
+    /// Generate X25519 keypair
+    static func generateKeypair() -> (privateKey: Curve25519.KeyAgreement.PrivateKey, publicKey: Curve25519.KeyAgreement.PublicKey) {
+        let privateKey = Curve25519.KeyAgreement.PrivateKey()
+        return (privateKey, privateKey.publicKey)
+    }
+
+    // MARK: - Serialization
+
+    /// Serialize X25519 private key to 32 raw bytes
+    static func serializePrivate(_ key: Curve25519.KeyAgreement.PrivateKey) -> Data {
+        key.rawData  // 32 bytes
+    }
+
+    /// Serialize X25519 public key to 32 raw bytes
+    static func serializePublic(_ key: Curve25519.KeyAgreement.PublicKey) -> Data {
+        key.rawData  // 32 bytes
+    }
+
+    /// Load X25519 private key from 32 raw bytes
+    static func loadPrivate(_ data: Data) throws -> Curve25519.KeyAgreement.PrivateKey {
+        guard data.count == 32 else {
+            throw CryptoError.invalidKeyData("X25519 private key must be 32 bytes")
+        }
+        return try Curve25519.KeyAgreement.PrivateKey(rawRepresentation: data)
+    }
+
+    /// Load X25519 public key from 32 raw bytes
+    static func loadPublic(_ data: Data) throws -> Curve25519.KeyAgreement.PublicKey {
+        guard data.count == 32 else {
+            throw CryptoError.invalidKeyData("X25519 public key must be 32 bytes")
+        }
+        return try Curve25519.KeyAgreement.PublicKey(rawRepresentation: data)
+    }
+
+    // MARK: - Diffie-Hellman
+
+    /// Perform X25519 DH key agreement. Returns 32-byte shared secret.
+    /// Matches Python: x25519_dh(private_key, public_key)
+    static func dh(_ privateKey: Curve25519.KeyAgreement.PrivateKey, _ publicKey: Curve25519.KeyAgreement.PublicKey) throws -> Data {
+        let sharedSecret = try privateKey.sharedSecretFromKeyAgreement(with: publicKey)
+        // Extract raw bytes from SharedSecret
+        return sharedSecret.withUnsafeBytes { Data($0) }
+    }
+
+    // MARK: - Ed25519 → X25519 Key Conversion
+
+    /// Convert Ed25519 private key to X25519 private key.
+    /// SHA-512(seed) → take first 32 bytes → clamp per RFC 7748
+    /// Matches Python: ed25519_private_to_x25519(ed_private)
+    static func fromEd25519Private(_ edPrivate: Curve25519.Signing.PrivateKey) throws -> Curve25519.KeyAgreement.PrivateKey {
+        let raw = edPrivate.rawData  // 32 bytes seed
+        // SHA-512 of the seed
+        let hash = SHA512.hash(data: raw)
+        var clamped = Data(hash.prefix(32))
+        // Clamp per RFC 7748
+        clamped[0] &= 248
+        clamped[31] &= 127
+        clamped[31] |= 64
+        return try Curve25519.KeyAgreement.PrivateKey(rawRepresentation: clamped)
+    }
+
+    /// Convert Ed25519 public key to X25519 public key.
+    /// Uses Montgomery birational map: u = (1+y)/(1-y) mod p
+    /// Matches Python: ed25519_public_to_x25519(ed_public)
+    static func fromEd25519Public(_ edPublic: Curve25519.Signing.PublicKey) throws -> Curve25519.KeyAgreement.PublicKey {
+        let x25519Bytes = FieldArithmetic.ed25519PublicToX25519(edPublic.rawData)
+        return try Curve25519.KeyAgreement.PublicKey(rawRepresentation: x25519Bytes)
+    }
+}
--- a/ios_client/EncryptedChat/Crypto/X3DH.swift
+++ b/ios_client/EncryptedChat/Crypto/X3DH.swift
@@ -0,0 +1,118 @@
+import Foundation
+import CryptoKit
+
+/// X3DH key agreement protocol (Signal Protocol)
+enum X3DH {
+
+    // MARK: - Pre-Key Generation
+
+    /// Generate a signed pre-key (SPK).
+    /// Returns (private, public, signature, id).
+    /// Matches Python: generate_signed_prekey(identity_private)
+    static func generateSignedPrekey(
+        identityPrivate: Curve25519.Signing.PrivateKey
+    ) throws -> (privateKey: Curve25519.KeyAgreement.PrivateKey,
+                  publicKey: Curve25519.KeyAgreement.PublicKey,
+                  signature: Data,
+                  id: String) {
+        let (spkPriv, spkPub) = X25519Crypto.generateKeypair()
+        let spkPubBytes = X25519Crypto.serializePublic(spkPub)
+        let signature = try Ed25519Crypto.sign(identityPrivate, data: spkPubBytes)
+        return (spkPriv, spkPub, signature, UUID().uuidString)
+    }
+
+    /// Generate a batch of one-time pre-keys.
+    /// Matches Python: generate_one_time_prekeys(count=50)
+    static func generateOneTimePrekeys(count: Int = 50) -> [(privateKey: Curve25519.KeyAgreement.PrivateKey,
+                                                               publicKey: Curve25519.KeyAgreement.PublicKey,
+                                                               id: String)] {
+        (0..<count).map { _ in
+            let (priv, pub) = X25519Crypto.generateKeypair()
+            return (priv, pub, UUID().uuidString)
+        }
+    }
+
+    // MARK: - X3DH Initiate (Alice)
+
+    /// Initiator side of X3DH.
+    /// Returns (sharedSecret, ephemeralPrivate, ephemeralPublic).
+    /// Matches Python: x3dh_initiate(ik_private_ed, ik_public_remote_ed, spk_remote, spk_signature, opk_remote?)
+    static func initiate(
+        ikPrivateEd: Curve25519.Signing.PrivateKey,
+        ikPublicRemoteEd: Curve25519.Signing.PublicKey,
+        spkRemote: Curve25519.KeyAgreement.PublicKey,
+        spkSignature: Data,
+        opkRemote: Curve25519.KeyAgreement.PublicKey? = nil
+    ) throws -> (sharedSecret: Data,
+                  ephemeralPrivate: Curve25519.KeyAgreement.PrivateKey,
+                  ephemeralPublic: Curve25519.KeyAgreement.PublicKey) {
+        // Verify SPK signature
+        let spkRemoteBytes = X25519Crypto.serializePublic(spkRemote)
+        guard Ed25519Crypto.verify(ikPublicRemoteEd, signature: spkSignature, data: spkRemoteBytes) else {
+            throw CryptoError.x3dhFailed("Invalid SPK signature")
+        }
+
+        // Convert identity keys to X25519
+        let ikX25519Private = try X25519Crypto.fromEd25519Private(ikPrivateEd)
+        let ikX25519Remote = try X25519Crypto.fromEd25519Public(ikPublicRemoteEd)
+
+        // Generate ephemeral keypair
+        let (ekPriv, ekPub) = X25519Crypto.generateKeypair()
+
+        // DH computations
+        let dh1 = try X25519Crypto.dh(ikX25519Private, spkRemote)   // IK_A, SPK_B
+        let dh2 = try X25519Crypto.dh(ekPriv, ikX25519Remote)        // EK_A, IK_B
+        let dh3 = try X25519Crypto.dh(ekPriv, spkRemote)             // EK_A, SPK_B
+
+        var dhConcat = dh1 + dh2 + dh3
+        if let opk = opkRemote {
+            let dh4 = try X25519Crypto.dh(ekPriv, opk)               // EK_A, OPK_B
+            dhConcat += dh4
+        }
+
+        // Derive shared secret
+        let sharedSecret = CryptoUtils.hkdfDerive(
+            inputKey: dhConcat,
+            salt: Data(repeating: 0x00, count: 32),
+            info: Data(Constants.x3dhInfo.utf8),
+            length: 32
+        )
+
+        return (sharedSecret, ekPriv, ekPub)
+    }
+
+    // MARK: - X3DH Respond (Bob)
+
+    /// Responder side of X3DH.
+    /// Returns sharedSecret.
+    /// Matches Python: x3dh_respond(ik_private_ed, spk_private, ik_remote_ed, ek_remote, opk_private?)
+    static func respond(
+        ikPrivateEd: Curve25519.Signing.PrivateKey,
+        spkPrivate: Curve25519.KeyAgreement.PrivateKey,
+        ikRemoteEd: Curve25519.Signing.PublicKey,
+        ekRemote: Curve25519.KeyAgreement.PublicKey,
+        opkPrivate: Curve25519.KeyAgreement.PrivateKey? = nil
+    ) throws -> Data {
+        let ikX25519Private = try X25519Crypto.fromEd25519Private(ikPrivateEd)
+        let ikX25519Remote = try X25519Crypto.fromEd25519Public(ikRemoteEd)
+
+        let dh1 = try X25519Crypto.dh(spkPrivate, ikX25519Remote)   // SPK_B, IK_A
+        let dh2 = try X25519Crypto.dh(ikX25519Private, ekRemote)     // IK_B, EK_A
+        let dh3 = try X25519Crypto.dh(spkPrivate, ekRemote)          // SPK_B, EK_A
+
+        var dhConcat = dh1 + dh2 + dh3
+        if let opk = opkPrivate {
+            let dh4 = try X25519Crypto.dh(opk, ekRemote)             // OPK_B, EK_A
+            dhConcat += dh4
+        }
+
+        let sharedSecret = CryptoUtils.hkdfDerive(
+            inputKey: dhConcat,
+            salt: Data(repeating: 0x00, count: 32),
+            info: Data(Constants.x3dhInfo.utf8),
+            length: 32
+        )
+
+        return sharedSecret
+    }
+}
--- a/ios_client/EncryptedChat/Models/Conversation.swift
+++ b/ios_client/EncryptedChat/Models/Conversation.swift
@@ -0,0 +1,46 @@
+import Foundation
+
+struct Conversation: Identifiable, Equatable {
+    let id: String
+    var name: String?
+    var members: [ConversationMember]
+    var createdBy: String?
+    var avatarFile: String?
+    var unreadCount: Int
+    var isFavorite: Bool
+    var lastMessageTime: Date?
+
+    var isGroup: Bool {
+        name != nil || members.count > 2
+    }
+
+    /// Display name: group name, or DM partner username
+    func displayName(currentUserId: String) -> String {
+        if let name = name, !name.isEmpty {
+            return name
+        }
+        // DM: show the other person's name
+        if let other = members.first(where: { $0.userId != currentUserId }) {
+            return other.username
+        }
+        return "Unknown"
+    }
+
+    /// DM partner user ID (nil for groups)
+    func dmPartnerId(currentUserId: String) -> String? {
+        guard !isGroup else { return nil }
+        return members.first(where: { $0.userId != currentUserId })?.userId
+    }
+
+    static func == (lhs: Conversation, rhs: Conversation) -> Bool {
+        lhs.id == rhs.id
+    }
+}
+
+struct ConversationMember: Identifiable, Equatable, Codable {
+    let userId: String
+    var username: String
+    var email: String
+
+    var id: String { userId }
+}
--- a/ios_client/EncryptedChat/Models/DeviceBundle.swift
+++ b/ios_client/EncryptedChat/Models/DeviceBundle.swift
@@ -0,0 +1,43 @@
+import Foundation
+
+/// Key bundle for one device, used in X3DH
+struct DeviceBundle {
+    let deviceId: String
+    let identityKey: Data      // Ed25519 public key (32 bytes)
+    let spk: Data              // X25519 public key (32 bytes)
+    let spkSignature: Data     // Ed25519 signature (64 bytes)
+    let spkId: String
+    let opk: Data?             // X25519 public key (32 bytes), optional
+    let opkId: String?
+
+    /// Parse from server response dictionary
+    static func fromDict(_ dict: [String: Any]) throws -> DeviceBundle {
+        guard let deviceId = dict["device_id"] as? String,
+              let ikHex = dict["identity_key"] as? String,
+              let ik = Data(hexString: ikHex),
+              let spkHex = dict["spk"] as? String,
+              let spk = Data(hexString: spkHex),
+              let spkSigHex = dict["spk_signature"] as? String,
+              let spkSig = Data(hexString: spkSigHex),
+              let spkId = dict["spk_id"] as? String else {
+            throw ChatError.invalidData("Invalid device bundle")
+        }
+
+        var opk: Data?
+        var opkId: String?
+        if let opkHex = dict["opk"] as? String, let opkData = Data(hexString: opkHex) {
+            opk = opkData
+            opkId = dict["opk_id"] as? String
+        }
+
+        return DeviceBundle(
+            deviceId: deviceId,
+            identityKey: ik,
+            spk: spk,
+            spkSignature: spkSig,
+            spkId: spkId,
+            opk: opk,
+            opkId: opkId
+        )
+    }
+}
--- a/ios_client/EncryptedChat/Models/Invitation.swift
+++ b/ios_client/EncryptedChat/Models/Invitation.swift
@@ -0,0 +1,9 @@
+import Foundation
+
+struct Invitation: Identifiable {
+    let id: String              // invitation id (from server) or conversationId
+    let conversationId: String
+    let conversationName: String
+    let invitedBy: String
+    let invitedByUsername: String
+}
--- a/ios_client/EncryptedChat/Models/Message.swift
+++ b/ios_client/EncryptedChat/Models/Message.swift
@@ -0,0 +1,33 @@
+import Foundation
+
+struct Message: Identifiable, Equatable {
+    let id: String
+    let conversationId: String
+    let senderId: String
+    var senderUsername: String
+    let createdAt: Date
+    var text: String?
+    var replyTo: String?
+    var imageFileId: String?
+    var file: FileInfo?
+    var isDeleted: Bool
+    var readBy: Set<String>
+
+    /// Whether this is a self-sent message
+    func isMine(currentUserId: String) -> Bool {
+        senderId == currentUserId
+    }
+
+    static func == (lhs: Message, rhs: Message) -> Bool {
+        lhs.id == rhs.id
+    }
+}
+
+struct FileInfo: Equatable, Codable {
+    let fileId: String
+    let aesKey: String   // hex
+    let iv: String       // hex
+    let filename: String
+    let size: Int
+    let mimeType: String
+}
--- a/ios_client/EncryptedChat/Models/User.swift
+++ b/ios_client/EncryptedChat/Models/User.swift
@@ -0,0 +1,19 @@
+import Foundation
+
+struct User: Identifiable, Equatable {
+    let id: String
+    var username: String
+    var email: String
+    var identityKey: Data?  // Ed25519 public key (32 bytes)
+}
+
+struct UserProfile: Equatable {
+    var userId: String
+    var username: String?
+    var email: String?
+    var phone: String?
+    var phoneVisible: Bool
+    var location: String?
+    var locationVisible: Bool
+    var avatarFile: String?
+}
--- a/ios_client/EncryptedChat/Network/ConnectionManager.swift
+++ b/ios_client/EncryptedChat/Network/ConnectionManager.swift
@@ -0,0 +1,188 @@
+import Foundation
+import Network
+
+/// TCP connection manager using Network.framework.
+/// Handles connection lifecycle, TLS, buffered reading (newline-delimited), and writing.
+actor ConnectionManager {
+
+    enum ConnectionState: Equatable {
+        case disconnected
+        case connecting
+        case connected
+        case failed(String)
+    }
+
+    private var connection: NWConnection?
+    private var receiveBuffer = Data()
+    private(set) var state: ConnectionState = .disconnected
+    private var stateCallback: ((ConnectionState) -> Void)?
+    private var messageStream: AsyncStream<[String: Any]>.Continuation?
+
+    /// Set a callback for connection state changes
+    func onStateChange(_ callback: @escaping (ConnectionState) -> Void) {
+        stateCallback = callback
+    }
+
+    // MARK: - Connect / Disconnect
+
+    /// Connect to server
+    func connect(host: String, port: UInt16, useTLS: Bool = false, tlsInsecure: Bool = false) async throws {
+        guard state == .disconnected || state != .connected else {
+            throw NetworkError.alreadyConnected
+        }
+
+        updateState(.connecting)
+
+        let nwHost = NWEndpoint.Host(host)
+        let nwPort = NWEndpoint.Port(rawValue: port)!
+
+        let params: NWParameters
+        if useTLS {
+            let tlsOptions = NWProtocolTLS.Options()
+            if tlsInsecure {
+                // Skip certificate verification (dev only)
+                sec_protocol_options_set_verify_block(
+                    tlsOptions.securityProtocolOptions,
+                    { _, _, completionHandler in completionHandler(true) },
+                    .main
+                )
+            }
+            params = NWParameters(tls: tlsOptions, tcp: .init())
+        } else {
+            params = .tcp
+        }
+
+        let conn = NWConnection(host: nwHost, port: nwPort, using: params)
+        self.connection = conn
+        self.receiveBuffer = Data()
+
+        return try await withCheckedThrowingContinuation { continuation in
+            conn.stateUpdateHandler = { [weak self] newState in
+                Task { [weak self] in
+                    guard let self = self else { return }
+                    switch newState {
+                    case .ready:
+                        await self.updateState(.connected)
+                        continuation.resume()
+                    case .failed(let error):
+                        await self.updateState(.failed(error.localizedDescription))
+                        continuation.resume(throwing: NetworkError.connectionFailed(error.localizedDescription))
+                    case .cancelled:
+                        await self.updateState(.disconnected)
+                    case .waiting(let error):
+                        await self.updateState(.failed(error.localizedDescription))
+                        continuation.resume(throwing: NetworkError.connectionFailed("Waiting: \(error.localizedDescription)"))
+                    default:
+                        break
+                    }
+                }
+            }
+            conn.start(queue: .global(qos: .userInitiated))
+        }
+    }
+
+    /// Disconnect from server
+    func disconnect() {
+        connection?.cancel()
+        connection = nil
+        receiveBuffer = Data()
+        updateState(.disconnected)
+        messageStream?.finish()
+        messageStream = nil
+    }
+
+    // MARK: - Send
+
+    /// Send raw data over the connection
+    func send(_ data: Data) async throws {
+        guard let connection = connection, state == .connected else {
+            throw NetworkError.notConnected
+        }
+
+        return try await withCheckedThrowingContinuation { continuation in
+            connection.send(content: data, completion: .contentProcessed { error in
+                if let error = error {
+                    continuation.resume(throwing: NetworkError.connectionFailed(error.localizedDescription))
+                } else {
+                    continuation.resume()
+                }
+            })
+        }
+    }
+
+    /// Send a protocol message (builds JSON + newline, sends)
+    func sendMessage(type: String, requestId: String? = nil, params: [String: Any] = [:]) async throws {
+        let data = try ProtocolHandler.buildRequest(type: type, requestId: requestId, params: params)
+        try await send(data)
+    }
+
+    // MARK: - Receive
+
+    /// Read one newline-delimited JSON message.
+    /// Returns nil on EOF / connection close.
+    func readMessage() async throws -> [String: Any]? {
+        while true {
+            // Check buffer for a complete line
+            if let newlineIndex = receiveBuffer.firstIndex(of: 0x0A) {
+                let lineData = receiveBuffer.prefix(through: newlineIndex)
+                receiveBuffer.removeSubrange(...newlineIndex)
+
+                // Check size
+                if lineData.count > Constants.maxMessageBytes {
+                    throw NetworkError.messageTooLarge
+                }
+
+                return try ProtocolHandler.parseMessage(Data(lineData))
+            }
+
+            // Buffer doesn't have a complete line — read more from the connection
+            guard let connection = connection else {
+                return nil
+            }
+
+            let chunk = try await receiveChunk(connection: connection)
+            guard let chunk = chunk else {
+                return nil  // EOF
+            }
+
+            receiveBuffer.append(chunk)
+
+            // Safety: if buffer exceeds max without a newline, drop it
+            if receiveBuffer.count > Constants.maxMessageBytes * 2 {
+                receiveBuffer = Data()
+                throw NetworkError.messageTooLarge
+            }
+        }
+    }
+
+    /// Read a chunk of data from the connection
+    private func receiveChunk(connection: NWConnection) async throws -> Data? {
+        return try await withCheckedThrowingContinuation { continuation in
+            connection.receive(minimumIncompleteLength: 1, maximumLength: 65536) { content, _, isComplete, error in
+                if let error = error {
+                    continuation.resume(throwing: NetworkError.connectionFailed(error.localizedDescription))
+                    return
+                }
+                if let content = content, !content.isEmpty {
+                    continuation.resume(returning: content)
+                } else if isComplete {
+                    continuation.resume(returning: nil)
+                } else {
+                    // No data and not complete — shouldn't happen but return nil
+                    continuation.resume(returning: nil)
+                }
+            }
+        }
+    }
+
+    // MARK: - State
+
+    var isConnected: Bool {
+        state == .connected
+    }
+
+    private func updateState(_ newState: ConnectionState) {
+        state = newState
+        stateCallback?(newState)
+    }
+}
--- a/ios_client/EncryptedChat/Network/ProtocolHandler.swift
+++ b/ios_client/EncryptedChat/Network/ProtocolHandler.swift
@@ -0,0 +1,90 @@
+import Foundation
+
+/// Newline-delimited JSON protocol handler.
+/// Matches Python: protocol.py build_request, build_response, parse_message, encode_binary, decode_binary
+enum ProtocolHandler {
+
+    /// Build a request message (newline-terminated JSON).
+    /// Matches Python: build_request(msg_type, request_id=None, **kwargs)
+    static func buildRequest(type: String, requestId: String? = nil, params: [String: Any] = [:]) throws -> Data {
+        var msg: [String: Any] = ["type": type]
+        if let requestId = requestId {
+            msg["request_id"] = requestId
+        }
+        // Merge params into msg
+        for (key, value) in params {
+            msg[key] = value
+        }
+
+        let jsonData = try JSONSerialization.data(withJSONObject: msg)
+        guard jsonData.count < Constants.maxMessageBytes else {
+            throw NetworkError.messageTooLarge
+        }
+        return jsonData + Data([0x0A])  // newline
+    }
+
+    /// Build a response message (newline-terminated JSON).
+    static func buildResponse(type: String, status: String, data: [String: Any]? = nil, requestId: String? = nil) throws -> Data {
+        var msg: [String: Any] = ["type": type, "status": status]
+        if let data = data {
+            msg["data"] = data
+        }
+        if let requestId = requestId {
+            msg["request_id"] = requestId
+        }
+
+        let jsonData = try JSONSerialization.data(withJSONObject: msg)
+        guard jsonData.count < Constants.maxMessageBytes else {
+            throw NetworkError.messageTooLarge
+        }
+        return jsonData + Data([0x0A])
+    }
+
+    /// Parse a single protocol message from bytes.
+    /// Matches Python: parse_message(line)
+    static func parseMessage(_ data: Data) throws -> [String: Any] {
+        let trimmed = data.trimmingNewlines()
+        guard !trimmed.isEmpty else {
+            throw NetworkError.protocolError("Empty message")
+        }
+        guard let obj = try JSONSerialization.jsonObject(with: trimmed) as? [String: Any] else {
+            throw NetworkError.protocolError("Message is not a JSON object")
+        }
+        return obj
+    }
+
+    /// Encode bytes to base64 string.
+    /// Matches Python: encode_binary(data)
+    static func encodeBinary(_ data: Data) -> String {
+        data.base64EncodedString(options: [])
+    }
+
+    /// Decode base64 string to bytes.
+    /// Matches Python: decode_binary(data)
+    static func decodeBinary(_ string: String) throws -> Data {
+        guard let data = Data(base64Encoded: string, options: .ignoreUnknownCharacters) else {
+            throw CryptoError.invalidBase64
+        }
+        return data
+    }
+
+    /// Generate a new request ID (UUID string).
+    static func newRequestId() -> String {
+        UUID().uuidString
+    }
+}
+
+// MARK: - Data Helpers
+
+private extension Data {
+    func trimmingNewlines() -> Data {
+        var data = self
+        while let last = data.last, last == 0x0A || last == 0x0D {
+            data.removeLast()
+        }
+        while let first = data.first, first == 0x0A || first == 0x0D {
+            data.removeFirst()
+        }
+        return data
+    }
+}
--- a/ios_client/EncryptedChat/Utilities/Constants.swift
+++ b/ios_client/EncryptedChat/Utilities/Constants.swift
@@ -0,0 +1,38 @@
+import Foundation
+
+enum Constants {
+    static let version = "0.8.2"
+    static let maxMessageBytes = 65536
+    static let maxImageBytes = 5 * 1024 * 1024      // 5 MB
+    static let maxFileBytes = 50 * 1024 * 1024       // 50 MB
+    static let imageChunkSize = 32768                 // 32 KB
+    static let selfDeviceId = "00000000-0000-0000-0000-000000000000"
+
+    static let opkReplenishThreshold = 20
+    static let opkBatchSize = 50
+    static let spkRotationDays = 7
+
+    static let maxSkip = 256
+    static let maxSenderKeySkip = 256
+
+    static let deviceBundleCacheTTL: TimeInterval = 300  // 5 minutes
+    static let sendReceiveTimeout: TimeInterval = 30
+    static let reconnectBaseDelay: TimeInterval = 1
+    static let reconnectMaxDelay: TimeInterval = 30
+
+    static let pbkdf2Iterations: UInt32 = 600_000
+    static let ecp1Magic = Data([0x45, 0x43, 0x50, 0x31])  // "ECP1"
+
+    // HKDF info/salt strings matching Python
+    static let x3dhInfo = "EncryptedChat_X3DH"
+    static let rootKeyInfo = "EncryptedChat_RootKey"
+    static let selfEncryptionSalt = "self_encryption"
+    static let selfEncryptionInfo = "EncryptedChat_SelfKey"
+    static let localStorageSalt = "local_storage"
+    static let localStorageInfo = "EncryptedChat_LocalStorage"
+    static let senderKeyChainInfo = "SenderKeyChain"
+
+    // Server connection defaults
+    static let defaultHost = "127.0.0.1"
+    static let defaultPort: UInt16 = 9999
+}
--- a/ios_client/EncryptedChat/Utilities/Extensions.swift
+++ b/ios_client/EncryptedChat/Utilities/Extensions.swift
@@ -0,0 +1,132 @@
+import Foundation
+import CryptoKit
+
+// MARK: - Data ↔ Hex
+
+extension Data {
+    /// Convert data to lowercase hex string
+    var hexString: String {
+        map { String(format: "%02x", $0) }.joined()
+    }
+
+    /// Initialize Data from a hex string
+    init?(hexString: String) {
+        let hex = hexString.lowercased()
+        guard hex.count % 2 == 0 else { return nil }
+        var data = Data(capacity: hex.count / 2)
+        var index = hex.startIndex
+        while index < hex.endIndex {
+            let nextIndex = hex.index(index, offsetBy: 2)
+            guard let byte = UInt8(hex[index..<nextIndex], radix: 16) else { return nil }
+            data.append(byte)
+            index = nextIndex
+        }
+        self = data
+    }
+
+    /// Generate random bytes
+    static func randomBytes(_ count: Int) -> Data {
+        var data = Data(count: count)
+        data.withUnsafeMutableBytes { ptr in
+            _ = SecRandomCopyBytes(kSecRandomDefault, count, ptr.baseAddress!)
+        }
+        return data
+    }
+}
+
+// MARK: - Data ↔ Base64 (Protocol Wire Format)
+
+extension Data {
+    /// Encode to standard base64 string (matching Python's base64.b64encode)
+    func base64EncodedString() -> String {
+        self.base64EncodedString(options: [])
+    }
+
+    /// Decode from base64 string
+    static func fromBase64(_ string: String) throws -> Data {
+        // Try standard base64 first, then URL-safe
+        if let data = Data(base64Encoded: string, options: .ignoreUnknownCharacters) {
+            return data
+        }
+        throw CryptoError.invalidBase64
+    }
+}
+
+// MARK: - UInt32 Big-Endian
+
+extension UInt32 {
+    var bigEndianData: Data {
+        var value = self.bigEndian
+        return Data(bytes: &value, count: 4)
+    }
+}
+
+// MARK: - CryptoKit Key → Data
+
+extension Curve25519.KeyAgreement.PublicKey {
+    var rawData: Data {
+        Data(rawRepresentation)
+    }
+}
+
+extension Curve25519.KeyAgreement.PrivateKey {
+    var rawData: Data {
+        Data(rawRepresentation)
+    }
+}
+
+extension Curve25519.Signing.PublicKey {
+    var rawData: Data {
+        Data(rawRepresentation)
+    }
+}
+
+extension Curve25519.Signing.PrivateKey {
+    var rawData: Data {
+        Data(rawRepresentation)
+    }
+}
+
+// MARK: - String helpers
+
+extension String {
+    /// Trim whitespace and newlines
+    var trimmed: String {
+        trimmingCharacters(in: .whitespacesAndNewlines)
+    }
+}
+
+// MARK: - Dictionary merge helper
+
+extension Dictionary where Key == String, Value == Any {
+    func string(for key: String) -> String? {
+        self[key] as? String
+    }
+
+    func int(for key: String) -> Int? {
+        if let i = self[key] as? Int { return i }
+        if let s = self[key] as? String, let i = Int(s) { return i }
+        return nil
+    }
+
+    func dict(for key: String) -> [String: Any]? {
+        self[key] as? [String: Any]
+    }
+
+    func array(for key: String) -> [[String: Any]]? {
+        self[key] as? [[String: Any]]
+    }
+
+    func data(for key: String) -> Data? {
+        if let hex = self[key] as? String {
+            return Data(hexString: hex)
+        }
+        return nil
+    }
+
+    func bool(for key: String) -> Bool? {
+        if let b = self[key] as? Bool { return b }
+        if let i = self[key] as? Int { return i != 0 }
+        return nil
+    }
+}
--- a/ios_client/EncryptedChat/ViewModels/AuthViewModel.swift
+++ b/ios_client/EncryptedChat/ViewModels/AuthViewModel.swift
@@ -0,0 +1,114 @@
+import Foundation
+import SwiftUI
+
+@Observable
+final class AuthViewModel {
+    var email = ""
+    var password = ""
+    var confirmPassword = ""
+    var username = ""
+    var confirmationCode = ""
+
+    var isLoading = false
+    var errorMessage: String?
+    var showConfirmation = false
+    var registrationMessage: String?
+
+    var serverHost = Constants.defaultHost
+    var serverPort = String(Constants.defaultPort)
+    var useTLS = false
+
+    enum AuthMode {
+        case login, register, pairing
+    }
+    var mode: AuthMode = .login
+
+    func login(appState: AppState) async {
+        guard !email.isEmpty, !password.isEmpty else {
+            errorMessage = "Email and password are required"
+            return
+        }
+
+        isLoading = true
+        errorMessage = nil
+
+        do {
+            let port = UInt16(serverPort) ?? Constants.defaultPort
+            try await appState.chatClient.connect(host: serverHost, port: port, useTLS: useTLS)
+        } catch {
+            isLoading = false
+            errorMessage = "Connection failed: \(error.localizedDescription)"
+            return
+        }
+
+        let (success, message) = await appState.chatClient.login(email: email, password: password)
+        isLoading = false
+
+        if success {
+            appState.email = email
+            appState.isLoggedIn = true
+            appState.connectionStatus = .connected
+            if let userId = await appState.chatClient.userId {
+                appState.currentUser = User(id: userId, username: await appState.chatClient.username, email: email)
+            }
+        } else {
+            errorMessage = message
+        }
+    }
+
+    func register(appState: AppState) async {
+        guard !email.isEmpty, !password.isEmpty, !username.isEmpty else {
+            errorMessage = "All fields are required"
+            return
+        }
+        guard password == confirmPassword else {
+            errorMessage = "Passwords don't match"
+            return
+        }
+
+        isLoading = true
+        errorMessage = nil
+
+        do {
+            let port = UInt16(serverPort) ?? Constants.defaultPort
+            try await appState.chatClient.connect(host: serverHost, port: port, useTLS: useTLS)
+        } catch {
+            isLoading = false
+            errorMessage = "Connection failed: \(error.localizedDescription)"
+            return
+        }
+
+        let (success, message) = await appState.chatClient.register(username: username, password: password, email: email)
+        isLoading = false
+
+        if success {
+            registrationMessage = message
+            showConfirmation = true
+        } else {
+            errorMessage = message
+        }
+    }
+
+    func confirmRegistration(appState: AppState) async {
+        guard !confirmationCode.isEmpty else {
+            errorMessage = "Enter the confirmation code"
+            return
+        }
+
+        isLoading = true
+        errorMessage = nil
+
+        let (success, message) = await appState.chatClient.confirmRegistration(
+            email: email, username: username, code: confirmationCode
+        )
+        isLoading = false
+
+        if success {
+            registrationMessage = message
+            // Auto-login after registration
+            await login(appState: appState)
+        } else {
+            errorMessage = message
+        }
+    }
+}
--- a/ios_client/EncryptedChat/ViewModels/ChatViewModel.swift
+++ b/ios_client/EncryptedChat/ViewModels/ChatViewModel.swift
@@ -0,0 +1,131 @@
+import Foundation
+import SwiftUI
+
+@Observable
+final class ChatViewModel {
+    var messages: [Message] = []
+    var isLoading = false
+    var isSending = false
+    var errorMessage: String?
+    var searchQuery = ""
+    var searchResults: [String] = []  // message IDs matching search
+    var currentSearchIndex = 0
+
+    private var notificationTask: Task<Void, Never>?
+
+    func loadMessages(convId: String, chatClient: ChatClient) async {
+        isLoading = true
+        messages = await chatClient.getMessages(convId: convId, limit: 50)
+        isLoading = false
+
+        // Mark as read
+        let unreadIds = messages.filter { !$0.isMine(currentUserId: await chatClient.userId ?? "") }.map(\.id)
+        if !unreadIds.isEmpty {
+            await chatClient.markRead(convId: convId, messageIds: unreadIds)
+        }
+    }
+
+    func loadOlderMessages(convId: String, chatClient: ChatClient) async {
+        let older = await chatClient.getMessages(convId: convId, limit: 50, offset: messages.count)
+        messages.insert(contentsOf: older, at: 0)
+    }
+
+    func sendMessage(convId: String, text: String, members: [ConversationMember],
+                     chatClient: ChatClient, replyTo: String? = nil) async {
+        guard !text.trimmingCharacters(in: .whitespacesAndNewlines).isEmpty else { return }
+
+        isSending = true
+        errorMessage = nil
+
+        let (success, msg) = await chatClient.sendMessage(
+            convId: convId, text: text, members: members, replyTo: replyTo
+        )
+
+        isSending = false
+
+        if !success {
+            errorMessage = msg
+        } else {
+            // Reload messages to get the sent message
+            await loadMessages(convId: convId, chatClient: chatClient)
+        }
+    }
+
+    func deleteMessage(messageId: String, convId: String, chatClient: ChatClient) async {
+        let success = await chatClient.deleteMessage(messageId: messageId, convId: convId)
+        if success {
+            messages.removeAll { $0.id == messageId }
+        }
+    }
+
+    func search(query: String) {
+        searchQuery = query
+        if query.isEmpty {
+            searchResults = []
+            currentSearchIndex = 0
+            return
+        }
+        let lower = query.lowercased()
+        searchResults = messages.filter { $0.text?.lowercased().contains(lower) == true }.map(\.id)
+        currentSearchIndex = searchResults.isEmpty ? 0 : searchResults.count - 1
+    }
+
+    func nextSearchResult() {
+        guard !searchResults.isEmpty else { return }
+        currentSearchIndex = (currentSearchIndex + 1) % searchResults.count
+    }
+
+    func prevSearchResult() {
+        guard !searchResults.isEmpty else { return }
+        currentSearchIndex = (currentSearchIndex - 1 + searchResults.count) % searchResults.count
+    }
+
+    func startNotificationListener(convId: String, chatClient: ChatClient) {
+        notificationTask?.cancel()
+        notificationTask = Task {
+            for await notification in await chatClient.notifications {
+                await handleNotification(notification, convId: convId, chatClient: chatClient)
+            }
+        }
+    }
+
+    @MainActor
+    private func handleNotification(_ notification: ChatNotification, convId: String, chatClient: ChatClient) {
+        switch notification {
+        case .newMessage(let data):
+            if data["conversation_id"] as? String == convId {
+                if let msg = Task.detached(priority: .userInitiated, operation: {
+                    await chatClient.decryptNotification(data)
+                }) as? Task<Message?, Never> {
+                    Task {
+                        if let message = await msg.value {
+                            messages.append(message)
+                            // Mark as read immediately since we're viewing this conv
+                            await chatClient.markRead(convId: convId, messageIds: [message.id])
+                        }
+                    }
+                }
+            }
+        case .messageDeleted(let data):
+            if let msgId = data["message_id"] as? String {
+                messages.removeAll { $0.id == msgId }
+            }
+        case .messagesRead(let data):
+            if let readUserId = data["user_id"] as? String,
+               let msgIds = data["message_ids"] as? [String] {
+                for i in messages.indices {
+                    if msgIds.contains(messages[i].id) {
+                        messages[i].readBy.insert(readUserId)
+                    }
+                }
+            }
+        default:
+            break
+        }
+    }
+
+    func stop() {
+        notificationTask?.cancel()
+        notificationTask = nil
+    }
+}
--- a/ios_client/EncryptedChat/ViewModels/ConversationListVM.swift
+++ b/ios_client/EncryptedChat/ViewModels/ConversationListVM.swift
@@ -0,0 +1,127 @@
+import Foundation
+import SwiftUI
+
+@Observable
+final class ConversationListVM {
+    var conversations: [Conversation] = []
+    var invitations: [Invitation] = []
+    var onlineUsers: Set<String> = []
+    var unreadCounts: [String: Int] = [:]
+    var favorites: Set<String> = []
+    var isLoading = false
+
+    private var notificationTask: Task<Void, Never>?
+
+    func load(chatClient: ChatClient, email: String) async {
+        isLoading = true
+
+        // Load favorites from disk
+        favorites = KeyStorage.loadFavorites(email: email)
+
+        // Fetch conversations
+        let convs = await chatClient.listConversations()
+        conversations = sortConversations(convs, currentUserId: await chatClient.userId ?? "")
+
+        // Populate unread counts from server
+        for conv in conversations where conv.unreadCount > 0 {
+            unreadCounts[conv.id] = conv.unreadCount
+        }
+
+        // Fetch invitations
+        invitations = await chatClient.listInvitations()
+
+        isLoading = false
+
+        // Start notification listener
+        startNotificationListener(chatClient: chatClient, email: email)
+    }
+
+    func refresh(chatClient: ChatClient) async {
+        let convs = await chatClient.listConversations()
+        conversations = sortConversations(convs, currentUserId: await chatClient.userId ?? "")
+        invitations = await chatClient.listInvitations()
+    }
+
+    func toggleFavorite(convId: String, email: String) {
+        if favorites.contains(convId) {
+            favorites.remove(convId)
+        } else {
+            favorites.insert(convId)
+        }
+        try? KeyStorage.saveFavorites(email: email, favorites: favorites)
+
+        // Re-sort
+        let userId = conversations.first?.createdBy ?? ""
+        conversations = sortConversations(conversations, currentUserId: userId)
+    }
+
+    func markConversationRead(convId: String) {
+        unreadCounts[convId] = 0
+    }
+
+    func incrementUnread(convId: String) {
+        unreadCounts[convId, default: 0] += 1
+    }
+
+    private func sortConversations(_ convs: [Conversation], currentUserId: String) -> [Conversation] {
+        var result = convs.map { conv -> Conversation in
+            var c = conv
+            c.isFavorite = favorites.contains(conv.id)
+            c.unreadCount = unreadCounts[conv.id] ?? conv.unreadCount
+            return c
+        }
+
+        result.sort { a, b in
+            // Favorites first
+            if a.isFavorite != b.isFavorite { return a.isFavorite }
+            // Online DMs next
+            let aOnline = a.dmPartnerId(currentUserId: currentUserId).map { onlineUsers.contains($0) } ?? false
+            let bOnline = b.dmPartnerId(currentUserId: currentUserId).map { onlineUsers.contains($0) } ?? false
+            if aOnline != bOnline { return aOnline }
+            // Alphabetical
+            return a.displayName(currentUserId: currentUserId).lowercased() < b.displayName(currentUserId: currentUserId).lowercased()
+        }
+
+        return result
+    }
+
+    private func startNotificationListener(chatClient: ChatClient, email: String) {
+        notificationTask?.cancel()
+        notificationTask = Task {
+            for await notification in await chatClient.notifications {
+                await handleNotification(notification, chatClient: chatClient, email: email)
+            }
+        }
+    }
+
+    @MainActor
+    private func handleNotification(_ notification: ChatNotification, chatClient: ChatClient, email: String) {
+        switch notification {
+        case .newMessage(let data):
+            if let convId = data["conversation_id"] as? String {
+                incrementUnread(convId: convId)
+            }
+        case .onlineUsers(let userIds):
+            onlineUsers = Set(userIds)
+        case .userOnline(let userId):
+            onlineUsers.insert(userId)
+        case .userOffline(let userId):
+            onlineUsers.remove(userId)
+        case .conversationCreated, .memberAdded, .memberRemoved, .conversationRenamed:
+            Task { await refresh(chatClient: chatClient) }
+        case .groupInvitation:
+            Task { invitations = await chatClient.listInvitations() }
+        case .connectionStateChanged(let connected):
+            if !connected {
+                // Could trigger auto-reconnect here
+            }
+        default:
+            break
+        }
+    }
+
+    func stop() {
+        notificationTask?.cancel()
+        notificationTask = nil
+    }
+}
--- a/ios_client/EncryptedChat/ViewModels/ProfileViewModel.swift
+++ b/ios_client/EncryptedChat/ViewModels/ProfileViewModel.swift
@@ -0,0 +1,66 @@
+import Foundation
+import SwiftUI
+
+@Observable
+final class ProfileViewModel {
+    var profile: UserProfile?
+    var avatarData: Data?
+    var isLoading = false
+    var isSaving = false
+    var errorMessage: String?
+
+    // Editable fields
+    var phone = ""
+    var phoneVisible = false
+    var location = ""
+    var locationVisible = false
+
+    func loadProfile(userId: String? = nil, chatClient: ChatClient) async {
+        isLoading = true
+        profile = await chatClient.getProfile(userId: userId)
+        isLoading = false
+
+        if let p = profile {
+            phone = p.phone ?? ""
+            phoneVisible = p.phoneVisible
+            location = p.location ?? ""
+            locationVisible = p.locationVisible
+        }
+
+        // Load avatar
+        let uid = userId ?? await chatClient.userId ?? ""
+        if !uid.isEmpty {
+            avatarData = await chatClient.getAvatar(userId: uid)
+        }
+    }
+
+    func saveProfile(chatClient: ChatClient) async {
+        isSaving = true
+        errorMessage = nil
+
+        let success = await chatClient.updateProfile(
+            phone: phone.isEmpty ? nil : phone,
+            phoneVisible: phoneVisible,
+            location: location.isEmpty ? nil : location,
+            locationVisible: locationVisible
+        )
+
+        isSaving = false
+
+        if !success {
+            errorMessage = "Failed to update profile"
+        }
+    }
+
+    func uploadAvatar(imageData: Data, chatClient: ChatClient) async {
+        isSaving = true
+        let success = await chatClient.updateAvatar(imageData: imageData)
+        isSaving = false
+
+        if success {
+            avatarData = imageData
+        } else {
+            errorMessage = "Failed to upload avatar"
+        }
+    }
+}
--- a/ios_client/EncryptedChat/Views/Auth/LoginView.swift
+++ b/ios_client/EncryptedChat/Views/Auth/LoginView.swift
@@ -0,0 +1,134 @@
+import SwiftUI
+
+struct LoginView: View {
+    @Bindable var viewModel: AuthViewModel
+    var appState: AppState
+
+    var body: some View {
+        NavigationStack {
+            ScrollView {
+                VStack(spacing: 20) {
+                    Image(systemName: "lock.shield.fill")
+                        .font(.system(size: 60))
+                        .foregroundStyle(.blue)
+                        .padding(.top, 40)
+
+                    Text("Encrypted Chat")
+                        .font(.largeTitle.bold())
+
+                    Text("End-to-end encrypted messaging")
+                        .font(.subheadline)
+                        .foregroundStyle(.secondary)
+
+                    VStack(spacing: 16) {
+                        // Server config
+                        DisclosureGroup("Server") {
+                            TextField("Host", text: $viewModel.serverHost)
+                                .textContentType(.URL)
+                                .autocapitalization(.none)
+                            TextField("Port", text: $viewModel.serverPort)
+                                .keyboardType(.numberPad)
+                            Toggle("Use TLS", isOn: $viewModel.useTLS)
+                        }
+                        .padding(.horizontal)
+
+                        TextField("Email", text: $viewModel.email)
+                            .textContentType(.emailAddress)
+                            .keyboardType(.emailAddress)
+                            .autocapitalization(.none)
+                            .textFieldStyle(.roundedBorder)
+
+                        SecureField("Password", text: $viewModel.password)
+                            .textContentType(.password)
+                            .textFieldStyle(.roundedBorder)
+
+                        if viewModel.mode == .register {
+                            TextField("Username", text: $viewModel.username)
+                                .textContentType(.username)
+                                .autocapitalization(.none)
+                                .textFieldStyle(.roundedBorder)
+
+                            SecureField("Confirm Password", text: $viewModel.confirmPassword)
+                                .textFieldStyle(.roundedBorder)
+                        }
+
+                        if let error = viewModel.errorMessage {
+                            Text(error)
+                                .foregroundStyle(.red)
+                                .font(.caption)
+                                .multilineTextAlignment(.center)
+                        }
+
+                        Button(action: {
+                            Task {
+                                if viewModel.mode == .login {
+                                    await viewModel.login(appState: appState)
+                                } else {
+                                    await viewModel.register(appState: appState)
+                                }
+                            }
+                        }) {
+                            if viewModel.isLoading {
+                                ProgressView()
+                                    .frame(maxWidth: .infinity)
+                            } else {
+                                Text(viewModel.mode == .login ? "Login" : "Register")
+                                    .frame(maxWidth: .infinity)
+                            }
+                        }
+                        .buttonStyle(.borderedProminent)
+                        .disabled(viewModel.isLoading)
+
+                        Button(viewModel.mode == .login ? "Don't have an account? Register" : "Already have an account? Login") {
+                            viewModel.mode = viewModel.mode == .login ? .register : .login
+                            viewModel.errorMessage = nil
+                        }
+                        .font(.caption)
+                    }
+                    .padding(.horizontal, 32)
+                }
+            }
+            .sheet(isPresented: $viewModel.showConfirmation) {
+                ConfirmationSheet(viewModel: viewModel, appState: appState)
+            }
+        }
+    }
+}
+
+struct ConfirmationSheet: View {
+    @Bindable var viewModel: AuthViewModel
+    var appState: AppState
+
+    var body: some View {
+        VStack(spacing: 20) {
+            Text("Confirm Registration")
+                .font(.title2.bold())
+
+            if let msg = viewModel.registrationMessage {
+                Text(msg)
+                    .font(.subheadline)
+                    .foregroundStyle(.secondary)
+                    .multilineTextAlignment(.center)
+            }
+
+            TextField("Confirmation Code", text: $viewModel.confirmationCode)
+                .textFieldStyle(.roundedBorder)
+                .keyboardType(.numberPad)
+
+            if let error = viewModel.errorMessage {
+                Text(error)
+                    .foregroundStyle(.red)
+                    .font(.caption)
+            }
+
+            Button("Confirm") {
+                Task {
+                    await viewModel.confirmRegistration(appState: appState)
+                }
+            }
+            .buttonStyle(.borderedProminent)
+            .disabled(viewModel.isLoading)
+        }
+        .padding(32)
+    }
+}
--- a/ios_client/EncryptedChat/Views/Auth/PairingView.swift
+++ b/ios_client/EncryptedChat/Views/Auth/PairingView.swift
@@ -0,0 +1,49 @@
+import SwiftUI
+
+struct PairingView: View {
+    var appState: AppState
+    @State private var pairingCode = ""
+    @State private var isWaiting = false
+    @State private var statusMessage: String?
+
+    var body: some View {
+        VStack(spacing: 24) {
+            Image(systemName: "iphone.and.arrow.forward")
+                .font(.system(size: 48))
+                .foregroundStyle(.blue)
+
+            Text("Device Pairing")
+                .font(.title2.bold())
+
+            Text("Enter the 8-digit pairing code shown on your other device.")
+                .font(.subheadline)
+                .foregroundStyle(.secondary)
+                .multilineTextAlignment(.center)
+
+            TextField("Pairing Code", text: $pairingCode)
+                .textFieldStyle(.roundedBorder)
+                .keyboardType(.numberPad)
+                .frame(maxWidth: 200)
+
+            if let status = statusMessage {
+                Text(status)
+                    .font(.caption)
+                    .foregroundStyle(status.contains("Error") ? .red : .secondary)
+            }
+
+            if isWaiting {
+                ProgressView("Waiting for authorization...")
+            }
+
+            Button("Start Pairing") {
+                Task {
+                    // Pairing implementation would go here
+                    statusMessage = "Pairing not yet implemented"
+                }
+            }
+            .buttonStyle(.borderedProminent)
+            .disabled(pairingCode.count != 8 || isWaiting)
+        }
+        .padding(32)
+    }
+}
--- a/ios_client/EncryptedChat/Views/Auth/RegisterView.swift
+++ b/ios_client/EncryptedChat/Views/Auth/RegisterView.swift
@@ -0,0 +1,4 @@
+import SwiftUI
+
+// Registration is handled within LoginView via mode toggle.
+// This file exists for potential future separation.
--- a/ios_client/EncryptedChat/Views/Chat/ChatView.swift
+++ b/ios_client/EncryptedChat/Views/Chat/ChatView.swift
@@ -0,0 +1,164 @@
+import SwiftUI
+
+struct ChatView: View {
+    let conversation: Conversation
+    var appState: AppState
+    @State private var viewModel = ChatViewModel()
+    @State private var inputText = ""
+    @State private var replyTo: Message?
+    @State private var showGroupInfo = false
+    @State private var showSearch = false
+    @State private var showDeleteConfirm = false
+
+    var body: some View {
+        VStack(spacing: 0) {
+            // Search bar
+            if showSearch {
+                SearchOverlayView(
+                    query: $viewModel.searchQuery,
+                    matchCount: viewModel.searchResults.count,
+                    currentIndex: viewModel.currentSearchIndex,
+                    onSearch: { viewModel.search(query: $0) },
+                    onNext: { viewModel.nextSearchResult() },
+                    onPrev: { viewModel.prevSearchResult() },
+                    onClose: { showSearch = false; viewModel.search(query: "") }
+                )
+            }
+
+            // Messages
+            ScrollViewReader { proxy in
+                ScrollView {
+                    LazyVStack(spacing: 8) {
+                        if viewModel.messages.count >= 50 {
+                            Button("Load older messages") {
+                                Task {
+                                    await viewModel.loadOlderMessages(convId: conversation.id, chatClient: appState.chatClient)
+                                }
+                            }
+                            .font(.caption)
+                            .padding()
+                        }
+
+                        ForEach(viewModel.messages) { message in
+                            MessageBubbleView(
+                                message: message,
+                                isMine: message.isMine(currentUserId: appState.currentUser?.id ?? ""),
+                                isHighlighted: viewModel.searchResults.contains(message.id),
+                                isCurrentSearchResult: viewModel.searchResults.indices.contains(viewModel.currentSearchIndex) &&
+                                    viewModel.searchResults[viewModel.currentSearchIndex] == message.id,
+                                onReply: { replyTo = message },
+                                onDelete: {
+                                    Task {
+                                        await viewModel.deleteMessage(messageId: message.id, convId: conversation.id, chatClient: appState.chatClient)
+                                    }
+                                }
+                            )
+                            .id(message.id)
+                        }
+                    }
+                    .padding(.horizontal)
+                    .padding(.vertical, 8)
+                }
+                .onChange(of: viewModel.messages.count) {
+                    if let lastId = viewModel.messages.last?.id {
+                        withAnimation {
+                            proxy.scrollTo(lastId, anchor: .bottom)
+                        }
+                    }
+                }
+            }
+
+            // Reply preview
+            if let reply = replyTo {
+                HStack {
+                    Rectangle()
+                        .fill(.blue)
+                        .frame(width: 3)
+                    VStack(alignment: .leading) {
+                        Text(reply.senderUsername)
+                            .font(.caption.bold())
+                        Text(reply.text ?? "")
+                            .font(.caption)
+                            .lineLimit(1)
+                    }
+                    Spacer()
+                    Button(action: { replyTo = nil }) {
+                        Image(systemName: "xmark.circle.fill")
+                            .foregroundStyle(.secondary)
+                    }
+                }
+                .padding(.horizontal)
+                .padding(.vertical, 6)
+                .background(.ultraThinMaterial)
+            }
+
+            // Input
+            MessageInputView(
+                text: $inputText,
+                isSending: viewModel.isSending,
+                onSend: {
+                    Task {
+                        let text = inputText
+                        inputText = ""
+                        let reply = replyTo?.id
+                        replyTo = nil
+                        await viewModel.sendMessage(
+                            convId: conversation.id,
+                            text: text,
+                            members: conversation.members,
+                            chatClient: appState.chatClient,
+                            replyTo: reply
+                        )
+                    }
+                }
+            )
+        }
+        .navigationTitle(conversation.displayName(currentUserId: appState.currentUser?.id ?? ""))
+        .navigationBarTitleDisplayMode(.inline)
+        .toolbar {
+            ToolbarItem(placement: .topBarTrailing) {
+                HStack(spacing: 16) {
+                    Button(action: { showSearch.toggle() }) {
+                        Image(systemName: "magnifyingglass")
+                    }
+
+                    if conversation.isGroup {
+                        Button(action: { showGroupInfo = true }) {
+                            Image(systemName: "info.circle")
+                        }
+                    }
+
+                    // Delete button
+                    if !conversation.isGroup || conversation.createdBy == appState.currentUser?.id {
+                        Button(action: { showDeleteConfirm = true }) {
+                            Image(systemName: "trash")
+                                .foregroundStyle(.red)
+                        }
+                    }
+                }
+            }
+        }
+        .alert("Delete Conversation?", isPresented: $showDeleteConfirm) {
+            Button("Cancel", role: .cancel) {}
+            Button("Delete", role: .destructive) {
+                Task {
+                    await appState.chatClient.deleteConversation(convId: conversation.id)
+                }
+            }
+        } message: {
+            Text(conversation.isGroup
+                 ? "This will remove all members and delete the conversation."
+                 : "This will remove you from the conversation.")
+        }
+        .sheet(isPresented: $showGroupInfo) {
+            GroupInfoView(conversation: conversation, appState: appState)
+        }
+        .task {
+            await viewModel.loadMessages(convId: conversation.id, chatClient: appState.chatClient)
+            viewModel.startNotificationListener(convId: conversation.id, chatClient: appState.chatClient)
+        }
+        .onDisappear {
+            viewModel.stop()
+        }
+    }
+}
--- a/ios_client/EncryptedChat/Views/Chat/ImageViewerView.swift
+++ b/ios_client/EncryptedChat/Views/Chat/ImageViewerView.swift
@@ -0,0 +1,43 @@
+import SwiftUI
+
+struct ImageViewerView: View {
+    let imageData: Data
+    @State private var scale: CGFloat = 1.0
+    @Environment(\.dismiss) private var dismiss
+
+    var body: some View {
+        NavigationStack {
+            GeometryReader { geo in
+                if let uiImage = UIImage(data: imageData) {
+                    Image(uiImage: uiImage)
+                        .resizable()
+                        .aspectRatio(contentMode: .fit)
+                        .scaleEffect(scale)
+                        .gesture(
+                            MagnifyGesture()
+                                .onChanged { value in
+                                    scale = value.magnification
+                                }
+                                .onEnded { _ in
+                                    withAnimation {
+                                        scale = max(1.0, min(scale, 5.0))
+                                    }
+                                }
+                        )
+                        .onTapGesture(count: 2) {
+                            withAnimation {
+                                scale = scale > 1 ? 1 : 2
+                            }
+                        }
+                        .frame(width: geo.size.width, height: geo.size.height)
+                }
+            }
+            .toolbar {
+                ToolbarItem(placement: .topBarTrailing) {
+                    Button("Done") { dismiss() }
+                }
+            }
+            .background(.black)
+        }
+    }
+}
--- a/ios_client/EncryptedChat/Views/Chat/MessageBubbleView.swift
+++ b/ios_client/EncryptedChat/Views/Chat/MessageBubbleView.swift
@@ -0,0 +1,123 @@
+import SwiftUI
+
+struct MessageBubbleView: View {
+    let message: Message
+    let isMine: Bool
+    var isHighlighted: Bool = false
+    var isCurrentSearchResult: Bool = false
+    var onReply: (() -> Void)?
+    var onDelete: (() -> Void)?
+
+    var body: some View {
+        HStack {
+            if isMine { Spacer(minLength: 60) }
+
+            VStack(alignment: isMine ? .trailing : .leading, spacing: 4) {
+                if !isMine {
+                    Text(message.senderUsername)
+                        .font(.caption.bold())
+                        .foregroundStyle(.secondary)
+                }
+
+                if message.isDeleted {
+                    Text("Message deleted")
+                        .font(.body.italic())
+                        .foregroundStyle(.secondary)
+                        .padding(12)
+                        .background(Color(.systemGray6))
+                        .clipShape(RoundedRectangle(cornerRadius: 16))
+                } else {
+                    // Reply reference
+                    if let replyTo = message.replyTo {
+                        HStack(spacing: 4) {
+                            Rectangle()
+                                .fill(.blue.opacity(0.5))
+                                .frame(width: 2)
+                            Text("Reply to message")
+                                .font(.caption)
+                                .foregroundStyle(.secondary)
+                        }
+                        .padding(.horizontal, 8)
+                    }
+
+                    // File card
+                    if let file = message.file {
+                        VStack(alignment: .leading, spacing: 4) {
+                            HStack {
+                                Image(systemName: "paperclip")
+                                Text(file.filename)
+                                    .lineLimit(1)
+                            }
+                            .font(.subheadline)
+
+                            Text(formatFileSize(file.size))
+                                .font(.caption)
+                                .foregroundStyle(.secondary)
+                        }
+                        .padding(12)
+                        .background(Color(.systemGray5))
+                        .clipShape(RoundedRectangle(cornerRadius: 12))
+                    }
+
+                    // Text content
+                    if let text = message.text {
+                        Text(text)
+                            .padding(12)
+                            .background(
+                                isMine ? Color.blue : Color(.systemGray5)
+                            )
+                            .foregroundStyle(isMine ? .white : .primary)
+                            .clipShape(RoundedRectangle(cornerRadius: 16))
+                    }
+
+                    // Timestamp
+                    Text(formatTime(message.createdAt))
+                        .font(.caption2)
+                        .foregroundStyle(.secondary)
+                }
+            }
+            .background(
+                isCurrentSearchResult ? Color.orange.opacity(0.3) :
+                isHighlighted ? Color.yellow.opacity(0.2) : Color.clear
+            )
+            .clipShape(RoundedRectangle(cornerRadius: 16))
+            .contextMenu {
+                if !message.isDeleted {
+                    Button(action: { onReply?() }) {
+                        Label("Reply", systemImage: "arrowshape.turn.up.left")
+                    }
+
+                    Button(action: {
+                        UIPasteboard.general.string = message.text ?? ""
+                    }) {
+                        Label("Copy", systemImage: "doc.on.doc")
+                    }
+
+                    if isMine {
+                        Button(role: .destructive, action: { onDelete?() }) {
+                            Label("Delete", systemImage: "trash")
+                        }
+                    }
+                }
+            }
+
+            if !isMine { Spacer(minLength: 60) }
+        }
+    }
+
+    private func formatTime(_ date: Date) -> String {
+        let formatter = DateFormatter()
+        if Calendar.current.isDateInToday(date) {
+            formatter.dateFormat = "HH:mm"
+        } else {
+            formatter.dateFormat = "MMM d, HH:mm"
+        }
+        return formatter.string(from: date)
+    }
+
+    private func formatFileSize(_ bytes: Int) -> String {
+        if bytes < 1024 { return "\(bytes) B" }
+        if bytes < 1024 * 1024 { return "\(bytes / 1024) KB" }
+        return String(format: "%.1f MB", Double(bytes) / (1024 * 1024))
+    }
+}
--- a/ios_client/EncryptedChat/Views/Chat/MessageInputView.swift
+++ b/ios_client/EncryptedChat/Views/Chat/MessageInputView.swift
@@ -0,0 +1,55 @@
+import SwiftUI
+import PhotosUI
+
+struct MessageInputView: View {
+    @Binding var text: String
+    let isSending: Bool
+    let onSend: () -> Void
+
+    @State private var showAttachMenu = false
+    @State private var selectedPhoto: PhotosPickerItem?
+
+    var body: some View {
+        HStack(spacing: 8) {
+            // Attach button
+            Menu {
+                Button(action: {}) {
+                    Label("Photo", systemImage: "photo")
+                }
+                Button(action: {}) {
+                    Label("File", systemImage: "doc")
+                }
+            } label: {
+                Image(systemName: "plus.circle.fill")
+                    .font(.title2)
+                    .foregroundStyle(.blue)
+            }
+
+            // Text field
+            TextField("Message", text: $text, axis: .vertical)
+                .textFieldStyle(.roundedBorder)
+                .lineLimit(1...5)
+                .onSubmit {
+                    if !text.trimmingCharacters(in: .whitespacesAndNewlines).isEmpty {
+                        onSend()
+                    }
+                }
+
+            // Send button
+            Button(action: onSend) {
+                if isSending {
+                    ProgressView()
+                        .scaleEffect(0.8)
+                } else {
+                    Image(systemName: "arrow.up.circle.fill")
+                        .font(.title2)
+                        .foregroundStyle(.blue)
+                }
+            }
+            .disabled(text.trimmingCharacters(in: .whitespacesAndNewlines).isEmpty || isSending)
+        }
+        .padding(.horizontal)
+        .padding(.vertical, 8)
+        .background(.ultraThinMaterial)
+    }
+}
--- a/ios_client/EncryptedChat/Views/Chat/SearchOverlayView.swift
+++ b/ios_client/EncryptedChat/Views/Chat/SearchOverlayView.swift
@@ -0,0 +1,46 @@
+import SwiftUI
+
+struct SearchOverlayView: View {
+    @Binding var query: String
+    let matchCount: Int
+    let currentIndex: Int
+    let onSearch: (String) -> Void
+    let onNext: () -> Void
+    let onPrev: () -> Void
+    let onClose: () -> Void
+
+    var body: some View {
+        HStack(spacing: 8) {
+            Image(systemName: "magnifyingglass")
+                .foregroundStyle(.secondary)
+
+            TextField("Search messages", text: $query)
+                .textFieldStyle(.roundedBorder)
+                .onChange(of: query) { _, newValue in
+                    onSearch(newValue)
+                }
+
+            if matchCount > 0 {
+                Text("\(currentIndex + 1)/\(matchCount)")
+                    .font(.caption)
+                    .foregroundStyle(.secondary)
+                    .fixedSize()
+
+                Button(action: onPrev) {
+                    Image(systemName: "chevron.up")
+                }
+                Button(action: onNext) {
+                    Image(systemName: "chevron.down")
+                }
+            }
+
+            Button(action: onClose) {
+                Image(systemName: "xmark.circle.fill")
+                    .foregroundStyle(.secondary)
+            }
+        }
+        .padding(.horizontal)
+        .padding(.vertical, 6)
+        .background(.ultraThinMaterial)
+    }
+}
--- a/ios_client/EncryptedChat/Views/Components/CircularAvatarView.swift
+++ b/ios_client/EncryptedChat/Views/Components/CircularAvatarView.swift
@@ -0,0 +1,46 @@
+import SwiftUI
+
+struct CircularAvatarView: View {
+    let name: String
+    var imageData: Data?
+    var size: CGFloat = 32
+    var isGroup: Bool = false
+
+    var body: some View {
+        if let imageData = imageData, let uiImage = UIImage(data: imageData) {
+            Image(uiImage: uiImage)
+                .resizable()
+                .aspectRatio(contentMode: .fill)
+                .frame(width: size, height: size)
+                .clipShape(Circle())
+        } else {
+            // Default: colored circle with initial letter
+            ZStack {
+                Circle()
+                    .fill(avatarColor)
+                    .frame(width: size, height: size)
+
+                Text(initial)
+                    .font(.system(size: size * 0.4, weight: .semibold))
+                    .foregroundStyle(.white)
+            }
+        }
+    }
+
+    private var initial: String {
+        String(name.prefix(1)).uppercased()
+    }
+
+    /// Deterministic color from name hash (matching Python gui_client behavior)
+    private var avatarColor: Color {
+        let colors: [Color] = [
+            .red, .orange, .yellow, .green, .mint,
+            .teal, .cyan, .blue, .indigo, .purple, .pink
+        ]
+        var hash = 0
+        for char in name.unicodeScalars {
+            hash = hash &* 31 &+ Int(char.value)
+        }
+        return colors[abs(hash) % colors.count]
+    }
+}
--- a/ios_client/EncryptedChat/Views/Components/ConnectionIndicator.swift
+++ b/ios_client/EncryptedChat/Views/Components/ConnectionIndicator.swift
@@ -0,0 +1,35 @@
+import SwiftUI
+
+struct ConnectionIndicator: View {
+    let status: ConnectionStatus
+
+    var body: some View {
+        HStack(spacing: 4) {
+            Circle()
+                .fill(statusColor)
+                .frame(width: 8, height: 8)
+
+            if status != .connected {
+                Text(statusText)
+                    .font(.caption2)
+                    .foregroundStyle(.secondary)
+            }
+        }
+    }
+
+    private var statusColor: Color {
+        switch status {
+        case .connected: return .green
+        case .connecting: return .orange
+        case .disconnected: return .red
+        }
+    }
+
+    private var statusText: String {
+        switch status {
+        case .connected: return ""
+        case .connecting: return "Connecting..."
+        case .disconnected: return "Disconnected"
+        }
+    }
+}
--- a/ios_client/EncryptedChat/Views/Components/OnlineDotOverlay.swift
+++ b/ios_client/EncryptedChat/Views/Components/OnlineDotOverlay.swift
@@ -0,0 +1,15 @@
+import SwiftUI
+
+struct OnlineDotOverlay: View {
+    var size: CGFloat = 12
+
+    var body: some View {
+        Circle()
+            .fill(.green)
+            .frame(width: size, height: size)
+            .overlay(
+                Circle()
+                    .stroke(.white, lineWidth: 2)
+            )
+    }
+}
--- a/ios_client/EncryptedChat/Views/Conversations/ConversationListView.swift
+++ b/ios_client/EncryptedChat/Views/Conversations/ConversationListView.swift
@@ -0,0 +1,99 @@
+import SwiftUI
+
+struct ConversationListView: View {
+    var appState: AppState
+    @Bindable var viewModel: ConversationListVM
+    @State private var showNewConversation = false
+    @State private var showProfile = false
+    @State private var selectedConversation: Conversation?
+
+    var body: some View {
+        NavigationStack {
+            List {
+                // Invitations section
+                if !viewModel.invitations.isEmpty {
+                    Section {
+                        ForEach(viewModel.invitations) { invitation in
+                            InvitationBanner(
+                                invitation: invitation,
+                                onAccept: {
+                                    Task {
+                                        let (success, _) = await appState.chatClient.acceptInvitation(convId: invitation.conversationId)
+                                        if success {
+                                            await viewModel.refresh(chatClient: appState.chatClient)
+                                        }
+                                    }
+                                },
+                                onDecline: {
+                                    Task {
+                                        await appState.chatClient.declineInvitation(convId: invitation.conversationId)
+                                        await viewModel.refresh(chatClient: appState.chatClient)
+                                    }
+                                }
+                            )
+                        }
+                    } header: {
+                        Text("Invitations")
+                    }
+                }
+
+                // Conversations section
+                Section {
+                    ForEach(viewModel.conversations) { conversation in
+                        NavigationLink(value: conversation) {
+                            ConversationRowView(
+                                conversation: conversation,
+                                currentUserId: appState.currentUser?.id ?? "",
+                                isOnline: conversation.dmPartnerId(currentUserId: appState.currentUser?.id ?? "")
+                                    .map { viewModel.onlineUsers.contains($0) } ?? false,
+                                unreadCount: viewModel.unreadCounts[conversation.id] ?? 0
+                            )
+                        }
+                        .contextMenu {
+                            Button(conversation.isFavorite ? "Remove from Favorites" : "Add to Favorites") {
+                                viewModel.toggleFavorite(convId: conversation.id, email: appState.email)
+                            }
+                        }
+                    }
+                }
+            }
+            .navigationTitle("Chats")
+            .navigationDestination(for: Conversation.self) { conversation in
+                ChatView(
+                    conversation: conversation,
+                    appState: appState
+                )
+            }
+            .toolbar {
+                ToolbarItem(placement: .topBarLeading) {
+                    ConnectionIndicator(status: appState.connectionStatus)
+                }
+                ToolbarItem(placement: .topBarTrailing) {
+                    HStack {
+                        Button(action: { showProfile = true }) {
+                            Image(systemName: "person.circle")
+                        }
+                        Button(action: { showNewConversation = true }) {
+                            Image(systemName: "square.and.pencil")
+                        }
+                    }
+                }
+            }
+            .refreshable {
+                await viewModel.refresh(chatClient: appState.chatClient)
+            }
+            .sheet(isPresented: $showNewConversation) {
+                NewConversationSheet(appState: appState) { convId in
+                    showNewConversation = false
+                    await viewModel.refresh(chatClient: appState.chatClient)
+                }
+            }
+            .sheet(isPresented: $showProfile) {
+                ProfileView(appState: appState, isOwnProfile: true)
+            }
+            .task {
+                await viewModel.load(chatClient: appState.chatClient, email: appState.email)
+            }
+        }
+    }
+}
--- a/ios_client/EncryptedChat/Views/Conversations/ConversationRowView.swift
+++ b/ios_client/EncryptedChat/Views/Conversations/ConversationRowView.swift
@@ -0,0 +1,58 @@
+import SwiftUI
+
+struct ConversationRowView: View {
+    let conversation: Conversation
+    let currentUserId: String
+    let isOnline: Bool
+    let unreadCount: Int
+
+    var body: some View {
+        HStack(spacing: 12) {
+            // Avatar
+            ZStack(alignment: .bottomTrailing) {
+                CircularAvatarView(
+                    name: conversation.displayName(currentUserId: currentUserId),
+                    size: 44,
+                    isGroup: conversation.isGroup
+                )
+
+                if isOnline && !conversation.isGroup {
+                    OnlineDotOverlay(size: 12)
+                }
+            }
+
+            VStack(alignment: .leading, spacing: 2) {
+                HStack {
+                    if conversation.isFavorite {
+                        Image(systemName: "star.fill")
+                            .font(.caption2)
+                            .foregroundStyle(.yellow)
+                    }
+
+                    Text(conversation.displayName(currentUserId: currentUserId))
+                        .font(unreadCount > 0 ? .body.bold() : .body)
+                        .lineLimit(1)
+                }
+
+                if conversation.isGroup {
+                    Text("\(conversation.members.count) members")
+                        .font(.caption)
+                        .foregroundStyle(.secondary)
+                }
+            }
+
+            Spacer()
+
+            if unreadCount > 0 {
+                Text("\(unreadCount)")
+                    .font(.caption2.bold())
+                    .foregroundStyle(.white)
+                    .padding(.horizontal, 8)
+                    .padding(.vertical, 2)
+                    .background(Color.blue)
+                    .clipShape(Capsule())
+            }
+        }
+        .padding(.vertical, 4)
+    }
+}
--- a/ios_client/EncryptedChat/Views/Conversations/NewConversationSheet.swift
+++ b/ios_client/EncryptedChat/Views/Conversations/NewConversationSheet.swift
@@ -0,0 +1,100 @@
+import SwiftUI
+
+struct NewConversationSheet: View {
+    var appState: AppState
+    var onCreated: (String) async -> Void
+
+    @State private var email = ""
+    @State private var groupName = ""
+    @State private var isGroup = false
+    @State private var memberEmails: [String] = [""]
+    @State private var isLoading = false
+    @State private var errorMessage: String?
+    @Environment(\.dismiss) private var dismiss
+
+    var body: some View {
+        NavigationStack {
+            Form {
+                Section {
+                    Toggle("Create Group", isOn: $isGroup)
+
+                    if isGroup {
+                        TextField("Group Name", text: $groupName)
+                    }
+                }
+
+                Section(isGroup ? "Members" : "Recipient") {
+                    if isGroup {
+                        ForEach(memberEmails.indices, id: \.self) { index in
+                            TextField("Email", text: $memberEmails[index])
+                                .textContentType(.emailAddress)
+                                .keyboardType(.emailAddress)
+                                .autocapitalization(.none)
+                        }
+                        Button("Add Member") {
+                            memberEmails.append("")
+                        }
+                    } else {
+                        TextField("Email", text: $email)
+                            .textContentType(.emailAddress)
+                            .keyboardType(.emailAddress)
+                            .autocapitalization(.none)
+                    }
+                }
+
+                if let error = errorMessage {
+                    Section {
+                        Text(error)
+                            .foregroundStyle(.red)
+                    }
+                }
+            }
+            .navigationTitle("New Conversation")
+            .navigationBarTitleDisplayMode(.inline)
+            .toolbar {
+                ToolbarItem(placement: .cancellationAction) {
+                    Button("Cancel") { dismiss() }
+                }
+                ToolbarItem(placement: .confirmationAction) {
+                    Button("Create") {
+                        Task { await create() }
+                    }
+                    .disabled(isLoading)
+                }
+            }
+        }
+    }
+
+    private func create() async {
+        isLoading = true
+        errorMessage = nil
+
+        let emails: [String]
+        if isGroup {
+            emails = memberEmails.map { $0.trimmed }.filter { !$0.isEmpty }
+            guard !emails.isEmpty else {
+                errorMessage = "Add at least one member"
+                isLoading = false
+                return
+            }
+        } else {
+            guard !email.trimmed.isEmpty else {
+                errorMessage = "Enter an email address"
+                isLoading = false
+                return
+            }
+            emails = [email.trimmed]
+        }
+
+        let name = isGroup && !groupName.trimmed.isEmpty ? groupName.trimmed : nil
+        let (convId, message) = await appState.chatClient.createConversation(emails: emails, name: name)
+
+        isLoading = false
+
+        if let convId = convId {
+            await onCreated(convId)
+        } else {
+            errorMessage = message
+        }
+    }
+}
--- a/ios_client/EncryptedChat/Views/Groups/CreateGroupSheet.swift
+++ b/ios_client/EncryptedChat/Views/Groups/CreateGroupSheet.swift
@@ -0,0 +1,4 @@
+import SwiftUI
+
+// Group creation is handled within NewConversationSheet via the isGroup toggle.
+// This file exists for potential future separation.
--- a/ios_client/EncryptedChat/Views/Groups/GroupInfoView.swift
+++ b/ios_client/EncryptedChat/Views/Groups/GroupInfoView.swift
@@ -0,0 +1,123 @@
+import SwiftUI
+
+struct GroupInfoView: View {
+    let conversation: Conversation
+    var appState: AppState
+    @State private var showRenameSheet = false
+    @State private var showLeaveConfirm = false
+    @State private var newName = ""
+    @Environment(\.dismiss) private var dismiss
+
+    private var isCreator: Bool {
+        conversation.createdBy == appState.currentUser?.id
+    }
+
+    var body: some View {
+        NavigationStack {
+            List {
+                // Avatar section
+                Section {
+                    HStack {
+                        Spacer()
+                        VStack(spacing: 8) {
+                            CircularAvatarView(
+                                name: conversation.name ?? "Group",
+                                size: 64,
+                                isGroup: true
+                            )
+
+                            Text(conversation.name ?? "Group")
+                                .font(.title2.bold())
+
+                            Text("\(conversation.members.count) members")
+                                .font(.subheadline)
+                                .foregroundStyle(.secondary)
+                        }
+                        Spacer()
+                    }
+                    .listRowBackground(Color.clear)
+                }
+
+                // Actions
+                if isCreator {
+                    Section {
+                        Button("Rename Group") {
+                            newName = conversation.name ?? ""
+                            showRenameSheet = true
+                        }
+
+                        Button("Change Avatar") {
+                            // Photo picker would go here
+                        }
+                    }
+                }
+
+                // Members
+                Section("Members") {
+                    ForEach(conversation.members) { member in
+                        HStack {
+                            CircularAvatarView(name: member.username, size: 32, isGroup: false)
+
+                            VStack(alignment: .leading) {
+                                Text(member.username)
+                                    .font(.body)
+                                Text(member.email)
+                                    .font(.caption)
+                                    .foregroundStyle(.secondary)
+                            }
+
+                            Spacer()
+
+                            if member.userId == conversation.createdBy {
+                                Text("Admin")
+                                    .font(.caption)
+                                    .foregroundStyle(.blue)
+                            }
+                        }
+                    }
+                }
+
+                // Leave / Delete
+                Section {
+                    Button("Leave Group", role: .destructive) {
+                        showLeaveConfirm = true
+                    }
+
+                    if isCreator {
+                        Button("Delete Group", role: .destructive) {
+                            Task {
+                                await appState.chatClient.deleteConversation(convId: conversation.id)
+                                dismiss()
+                            }
+                        }
+                    }
+                }
+            }
+            .navigationTitle("Group Info")
+            .navigationBarTitleDisplayMode(.inline)
+            .toolbar {
+                ToolbarItem(placement: .topBarTrailing) {
+                    Button("Done") { dismiss() }
+                }
+            }
+            .alert("Leave Group?", isPresented: $showLeaveConfirm) {
+                Button("Cancel", role: .cancel) {}
+                Button("Leave", role: .destructive) {
+                    Task {
+                        await appState.chatClient.leaveGroup(convId: conversation.id)
+                        dismiss()
+                    }
+                }
+            }
+            .alert("Rename Group", isPresented: $showRenameSheet) {
+                TextField("Group Name", text: $newName)
+                Button("Cancel", role: .cancel) {}
+                Button("Rename") {
+                    Task {
+                        await appState.chatClient.renameConversation(convId: conversation.id, name: newName)
+                    }
+                }
+            }
+        }
+    }
+}
--- a/ios_client/EncryptedChat/Views/Groups/InvitationBanner.swift
+++ b/ios_client/EncryptedChat/Views/Groups/InvitationBanner.swift
@@ -0,0 +1,41 @@
+import SwiftUI
+
+struct InvitationBanner: View {
+    let invitation: Invitation
+    let onAccept: () -> Void
+    let onDecline: () -> Void
+
+    var body: some View {
+        VStack(alignment: .leading, spacing: 8) {
+            HStack {
+                Image(systemName: "envelope.badge")
+                    .foregroundStyle(.orange)
+
+                VStack(alignment: .leading) {
+                    Text(invitation.conversationName)
+                        .font(.body.bold())
+                    Text("Invited by \(invitation.invitedByUsername)")
+                        .font(.caption)
+                        .foregroundStyle(.secondary)
+                }
+
+                Spacer()
+            }
+
+            HStack(spacing: 12) {
+                Button("Accept") {
+                    onAccept()
+                }
+                .buttonStyle(.borderedProminent)
+                .controlSize(.small)
+
+                Button("Decline") {
+                    onDecline()
+                }
+                .buttonStyle(.bordered)
+                .controlSize(.small)
+            }
+        }
+        .padding(.vertical, 4)
+    }
+}
--- a/ios_client/EncryptedChat/Views/Profile/EditProfileView.swift
+++ b/ios_client/EncryptedChat/Views/Profile/EditProfileView.swift
@@ -0,0 +1,4 @@
+import SwiftUI
+
+// Profile editing is handled within ProfileView when isOwnProfile = true.
+// This file exists for potential future separation.
--- a/ios_client/EncryptedChat/Views/Profile/ProfileView.swift
+++ b/ios_client/EncryptedChat/Views/Profile/ProfileView.swift
@@ -0,0 +1,111 @@
+import SwiftUI
+
+struct ProfileView: View {
+    var appState: AppState
+    var isOwnProfile: Bool
+    var userId: String?
+    @State private var viewModel = ProfileViewModel()
+    @Environment(\.dismiss) private var dismiss
+
+    var body: some View {
+        NavigationStack {
+            Form {
+                // Avatar
+                Section {
+                    HStack {
+                        Spacer()
+                        VStack(spacing: 8) {
+                            if let avatarData = viewModel.avatarData,
+                               let uiImage = UIImage(data: avatarData) {
+                                Image(uiImage: uiImage)
+                                    .resizable()
+                                    .aspectRatio(contentMode: .fill)
+                                    .frame(width: 80, height: 80)
+                                    .clipShape(Circle())
+                            } else {
+                                CircularAvatarView(
+                                    name: viewModel.profile?.username ?? "?",
+                                    size: 80,
+                                    isGroup: false
+                                )
+                            }
+
+                            if isOwnProfile {
+                                Button("Change Photo") {
+                                    // Photo picker would go here
+                                }
+                                .font(.caption)
+                            }
+                        }
+                        Spacer()
+                    }
+                    .listRowBackground(Color.clear)
+                }
+
+                // Info
+                Section("Info") {
+                    if let username = viewModel.profile?.username {
+                        LabeledContent("Username", value: username)
+                    }
+                    if let email = viewModel.profile?.email {
+                        LabeledContent("Email", value: email)
+                    }
+                }
+
+                if isOwnProfile {
+                    // Editable fields
+                    Section("Contact") {
+                        TextField("Phone", text: $viewModel.phone)
+                            .keyboardType(.phonePad)
+                        Toggle("Phone visible to contacts", isOn: $viewModel.phoneVisible)
+
+                        TextField("Location", text: $viewModel.location)
+                        Toggle("Location visible to contacts", isOn: $viewModel.locationVisible)
+                    }
+                } else {
+                    // Read-only view
+                    if let phone = viewModel.profile?.phone, viewModel.profile?.phoneVisible == true {
+                        Section("Contact") {
+                            LabeledContent("Phone", value: phone)
+                        }
+                    }
+                    if let location = viewModel.profile?.location, viewModel.profile?.locationVisible == true {
+                        Section("Location") {
+                            LabeledContent("Location", value: location)
+                        }
+                    }
+                }
+
+                if let error = viewModel.errorMessage {
+                    Section {
+                        Text(error)
+                            .foregroundStyle(.red)
+                    }
+                }
+            }
+            .navigationTitle(isOwnProfile ? "My Profile" : "Profile")
+            .navigationBarTitleDisplayMode(.inline)
+            .toolbar {
+                ToolbarItem(placement: .topBarTrailing) {
+                    if isOwnProfile {
+                        Button("Save") {
+                            Task {
+                                await viewModel.saveProfile(chatClient: appState.chatClient)
+                                dismiss()
+                            }
+                        }
+                        .disabled(viewModel.isSaving)
+                    } else {
+                        Button("Done") { dismiss() }
+                    }
+                }
+                ToolbarItem(placement: .cancellationAction) {
+                    Button("Cancel") { dismiss() }
+                }
+            }
+            .task {
+                await viewModel.loadProfile(userId: userId, chatClient: appState.chatClient)
+            }
+        }
+    }
+}