Implement call encryption

Security fixes

frontend/src/core/calls/e2eeWorker.ts

@@ -0,0 +1,100 @@
+/**
+ * E2EE Worker for WebRTC Insertable Streams
+ * Conditionally encrypts or decrypts encoded audio frames using AES-GCM
+ */
+
+export interface EncodedFrame {
+    data: Uint8Array;
+}
+
+export interface WorkerOptions {
+    key: CryptoKey;
+    mode: 'encrypt' | 'decrypt';
+    sessionId?: string; // For replay protection
+}
+
+addEventListener("rtctransform", (event) => {
+    const { transformer } = event;
+    const { readable, writable } = transformer;
+    const { key, mode, sessionId } = transformer.options as WorkerOptions;
+    
+    // Generate a random base IV once per transform session
+    const ivBase = crypto.getRandomValues(new Uint8Array(8)); // 8 random bytes
+    let frameCounter = 0;
+    let lastFrameTime = 0;
+    const FRAME_WINDOW_MS = 5000; // 5 second window for replay protection
+
+    async function transform(encodedFrame: EncodedFrame, controller: TransformStreamDefaultController<EncodedFrame>) {
+        try {
+            const currentTime = Date.now();
+            
+            // Replay protection for decryption
+            if (mode === 'decrypt') {
+                // Simple time-based replay protection
+                if (currentTime - lastFrameTime > FRAME_WINDOW_MS && lastFrameTime > 0) {
+                    console.warn("Potential replay attack detected - frame outside time window");
+                    controller.error(new Error("Replay attack detected"));
+                    return;
+                }
+                lastFrameTime = currentTime;
+            }
+            
+            // Create IV: 8 random bytes + 4-byte frame counter
+            const iv = new Uint8Array(12);
+            iv.set(ivBase, 0); // Copy random base
+            const view = new DataView(iv.buffer);
+            view.setUint32(8, frameCounter++, false); // Big-endian frame counter
+            
+            const data = new Uint8Array(encodedFrame.data);
+            
+            // Add frame metadata for authentication
+            const frameMetadata = new TextEncoder().encode(JSON.stringify({
+                frameNumber: frameCounter - 1,
+                timestamp: currentTime,
+                sessionId: sessionId || 'default'
+            }));
+            
+            // Combine frame data with metadata
+            const combinedData = new Uint8Array(data.length + frameMetadata.length);
+            combinedData.set(frameMetadata, 0);
+            combinedData.set(data, frameMetadata.length);
+            
+            const params: AesGcmParams = { name: 'AES-GCM', iv };
+            
+            let result: ArrayBuffer;
+            if (mode === 'encrypt') {
+                result = await crypto.subtle.encrypt(params, key, combinedData);
+            } else {
+                result = await crypto.subtle.decrypt(params, key, combinedData);
+                
+                // Verify frame metadata on decryption
+                const decryptedData = new Uint8Array(result);
+                const metadataLength = frameMetadata.length;
+                const extractedMetadata = decryptedData.slice(0, metadataLength);
+                const extractedData = decryptedData.slice(metadataLength);
+                
+                try {
+                    const metadata = JSON.parse(new TextDecoder().decode(extractedMetadata));
+                    if (metadata.frameNumber !== frameCounter - 1) {
+                        throw new Error("Frame sequence number mismatch");
+                    }
+                    result = extractedData.buffer;
+                } catch (parseError) {
+                    console.warn("Frame authentication failed:", parseError);
+                    controller.error(new Error("Frame authentication failed"));
+                    return;
+                }
+            }
+            
+            encodedFrame.data = new Uint8Array(result);
+            controller.enqueue(encodedFrame);
+        } catch (e) {
+            console.error(`E2EE ${mode} failed:`, e);
+            controller.error(new Error(`E2EE ${mode} failed`));
+        }
+    }
+
+    readable
+        .pipeThrough(new TransformStream({ transform }))
+        .pipeTo(writable);
+});

frontend/src/core/calls/encryption.ts

@@ -0,0 +1,236 @@
+import { importAesGcmKey, aesGcmEncrypt, aesGcmDecrypt } from "@/utils/crypto/symmetric";
+import { randomBytes } from "@/utils/crypto/kdf";
+import { b64, ub64 } from "@/utils/utils";
+import { ecdhSharedSecret, deriveWrappingKey } from "@/utils/crypto/asymmetric";
+import { getCurrentKeys } from "@/core/api/authApi";
+
+export interface CallSessionKey {
+    key: Uint8Array;
+    hash: string; // For emoji display
+}
+
+export interface CallKeyExchange {
+    type: "call_key_exchange";
+    sessionKeyHash: string;
+    encryptedSessionKey: EncryptedCallMessage;
+}
+
+export interface EncryptedCallMessage {
+    iv: string;
+    ciphertext: string;
+    salt: string;
+    iv2: string;
+    wrappedSessionKey: string;
+}
+
+/**
+ * Generate a call session key (for initiator only)
+ */
+export async function generateCallSessionKey(): Promise<CallSessionKey> {
+    // Generate session key material
+    const sessionKeyMaterial = randomBytes(32);
+    
+    // Generate hash for emoji display (first 4 bytes of SHA-256 hash)
+    const hashBuffer = await crypto.subtle.digest("SHA-256", sessionKeyMaterial.buffer as ArrayBuffer);
+    const hash = b64(new Uint8Array(hashBuffer.slice(0, 4)));
+    
+    return {
+        key: sessionKeyMaterial,
+        hash
+    };
+}
+
+/**
+ * Rotate a session key by generating a completely new key
+ * This provides forward secrecy for long-running calls
+ */
+export async function rotateCallSessionKey(_currentSessionKey: CallSessionKey): Promise<CallSessionKey> {
+    // Generate new session key material (completely independent of current key)
+    const newSessionKeyMaterial = randomBytes(32);
+    
+    // Generate new hash for emoji display
+    const hashBuffer = await crypto.subtle.digest("SHA-256", newSessionKeyMaterial.buffer as ArrayBuffer);
+    const newHash = b64(new Uint8Array(hashBuffer.slice(0, 4)));
+    
+    return {
+        key: newSessionKeyMaterial,
+        hash: newHash
+    };
+}
+
+/**
+ * Create session key from hash (for backward compatibility)
+ * @deprecated Use deriveCallSessionKeyFromSharedSecret instead
+ */
+export async function createCallSessionKeyFromHash(hash: string): Promise<CallSessionKey> {
+    // For backward compatibility, generate a deterministic key from the hash
+    const hashBytes = ub64(hash);
+    const sessionKey = new Uint8Array(32);
+    
+    // Repeat the hash bytes to fill 32 bytes
+    for (let i = 0; i < 32; i++) {
+        sessionKey[i] = hashBytes[i % hashBytes.length];
+    }
+    
+    return {
+        key: sessionKey,
+        hash
+    };
+}
+
+/**
+ * Derive session key from ECDH shared secret and session key hash
+ * This creates a deterministic but cryptographically secure key
+ */
+export async function deriveCallSessionKeyFromSharedSecret(
+    sharedSecret: Uint8Array, 
+    sessionKeyHash: string,
+    isInitiator: boolean
+): Promise<CallSessionKey> {
+    // Use HKDF to derive the session key from the shared secret
+    // Include the session key hash and role to ensure uniqueness
+    const info = new TextEncoder().encode(`call-session-${sessionKeyHash}-${isInitiator ? 'initiator' : 'receiver'}`);
+    const salt = new Uint8Array(32); // Zero salt for deterministic derivation
+    
+    // Import the shared secret as a raw key for HKDF
+    const sharedKey = await crypto.subtle.importKey(
+        'raw',
+        sharedSecret.buffer as ArrayBuffer,
+        { name: 'HKDF' },
+        false,
+        ['deriveKey']
+    );
+    
+    // Derive the session key using HKDF
+    const sessionKey = await crypto.subtle.deriveKey(
+        {
+            name: 'HKDF',
+            hash: 'SHA-256',
+            salt: salt,
+            info: info
+        },
+        sharedKey,
+        { name: 'AES-GCM', length: 256 },
+        true, // Make the key extractable so we can export it
+        ['encrypt', 'decrypt']
+    );
+    
+    // Export the raw key material
+    const sessionKeyMaterial = await crypto.subtle.exportKey('raw', sessionKey);
+    
+    return {
+        key: new Uint8Array(sessionKeyMaterial),
+        hash: sessionKeyHash
+    };
+}
+
+/**
+ * Encrypt a call signaling message with the session key
+ */
+export async function encryptCallMessage(message: any, sessionKey: Uint8Array): Promise<EncryptedCallMessage> {
+    const messageKey = await importAesGcmKey(sessionKey);
+    const encrypted = await aesGcmEncrypt(messageKey, new TextEncoder().encode(JSON.stringify(message)));
+    
+    return {
+        iv: b64(encrypted.iv),
+        ciphertext: b64(encrypted.ciphertext),
+        salt: "", // Not used for message encryption, only for key wrapping
+        iv2: "",
+        wrappedSessionKey: ""
+    };
+}
+
+/**
+ * Decrypt a call signaling message
+ */
+export async function decryptCallMessage(encryptedMessage: EncryptedCallMessage, sessionKey: Uint8Array): Promise<any> {
+    const messageKey = await importAesGcmKey(sessionKey);
+    const decrypted = await aesGcmDecrypt(messageKey, ub64(encryptedMessage.iv), ub64(encryptedMessage.ciphertext));
+    return JSON.parse(new TextDecoder().decode(decrypted));
+}
+
+/**
+ * Generate 4 emojis representing the call session key
+ */
+export function generateCallEmojis(sessionKeyHash: string): string[] {
+    // Convert hash to numbers and map to emoji ranges
+    const hashBytes = new Uint8Array(ub64(sessionKeyHash));
+    const emojis: string[] = [];
+    
+    // Different emoji categories for variety
+    const emojiSets = [
+        ["🎵", "🎶", "🎤", "🎧", "🎼", "🎹", "🥁", "🎺", "🎸", "🎻"], // Music
+        ["🔥", "💫", "⭐", "✨", "🌟", "💥", "⚡", "🌈", "🎆", "🎇"], // Energy
+        ["🚀", "🛸", "🛰️", "🌌", "🔭", "⚙️", "🔧", "⚡", "💡", "🔬"], // Tech/Space
+        ["🎭", "🎪", "🎨", "🎬", "📷", "🎥", "📺", "🎮", "🕹️", "🎯"]  // Entertainment
+    ];
+    
+    for (let i = 0; i < 4; i++) {
+        const set = emojiSets[i % emojiSets.length];
+        const index = hashBytes[i % hashBytes.length] % set.length;
+        emojis.push(set[index]);
+    }
+    
+    return emojis;
+}
+
+// HKDF info for CALL key wrapping (distinct from DM's info)
+const CALL_INFO = new Uint8Array([2]);
+
+export interface WrappedSessionKeyPayload {
+    salt: string; // b64 salt used in HKDF
+    iv2: string; // b64 IV used to wrap session key
+    wrapped: string; // b64 ciphertext of wrapped session key
+}
+
+/**
+ * Wrap a session key for a recipient using ECDH (X25519) and AES-GCM
+ */
+export async function wrapCallSessionKeyForRecipient(recipientPublicKeyB64: string, sessionKey: Uint8Array): Promise<WrappedSessionKeyPayload> {
+    const keys = getCurrentKeys();
+    if (!keys) throw new Error("Keys not initialized");
+
+    const salt = randomBytes(16);
+    const shared = ecdhSharedSecret(keys.privateKey, ub64(recipientPublicKeyB64));
+    const wkRaw = await deriveWrappingKey(shared, salt, CALL_INFO);
+    const wk = await importAesGcmKey(wkRaw);
+    const wrap = await aesGcmEncrypt(wk, sessionKey);
+    return {
+        salt: b64(salt),
+        iv2: b64(wrap.iv),
+        wrapped: b64(wrap.ciphertext)
+    };
+}
+
+/**
+ * Create a shared secret and derive session key for the receiver
+ */
+export async function createSharedSecretAndDeriveSessionKey(
+    senderPublicKeyB64: string,
+    sessionKeyHash: string,
+    isInitiator: boolean
+): Promise<CallSessionKey> {
+    const keys = getCurrentKeys();
+    if (!keys) throw new Error("Keys not initialized");
+
+    // Create shared secret using ECDH
+    const sharedSecret = ecdhSharedSecret(keys.privateKey, ub64(senderPublicKeyB64));
+    
+    // Derive the session key from the shared secret
+    return await deriveCallSessionKeyFromSharedSecret(sharedSecret, sessionKeyHash, isInitiator);
+}
+
+/**
+ * Unwrap a received session key using sender's public key
+ */
+export async function unwrapCallSessionKeyFromSender(senderPublicKeyB64: string, payload: WrappedSessionKeyPayload): Promise<Uint8Array> {
+    const keys = getCurrentKeys();
+    if (!keys) throw new Error("Keys not initialized");
+
+    const salt = ub64(payload.salt);
+    const shared = ecdhSharedSecret(keys.privateKey, ub64(senderPublicKeyB64));
+    const wkRaw = await deriveWrappingKey(shared, salt, CALL_INFO);
+    const wk = await importAesGcmKey(wkRaw);
+    const sessionKey = await aesGcmDecrypt(wk, ub64(payload.iv2), ub64(payload.wrapped));
+    return new Uint8Array(sessionKey);
+}

frontend/src/core/calls/signaling.ts

@@ -1,9 +1,10 @@
-import type { WebSocketMessage, CallSignalingData, CallInvite } from "@/core/types";
+import type { CallInvite, CallSignalingMessage } from "@/core/types";
 import * as WebRTC from "./webrtc";
 
 export interface CallState {
     receiveCall: (userId: number, username: string) => void;
     endCall: () => void;
+    setCallSessionKeyHash: (sessionKeyHash: string) => void;
 }
 
 export class CallSignalingHandler {
@@ -13,7 +14,7 @@ export class CallSignalingHandler {
         this.getState = getState;
     }
 
-    handleWebSocketMessage(message: WebSocketMessage<CallSignalingData>) {
+    handleWebSocketMessage(message: CallSignalingMessage) {
         if (message.type !== "call_signaling") {
             return;
         }
@@ -48,6 +49,9 @@ export class CallSignalingHandler {
             case "call_end":
                 this.handleCallEnd(data);
                 break;
+            case "call_session_key":
+                this.handleCallSessionKey(data);
+                break;
         }
     }
 
@@ -112,4 +116,14 @@ export class CallSignalingHandler {
         // End the call
         state.endCall();
     }
+
+    private handleCallSessionKey({ sessionKeyHash, data, ...message }: CallSignalingMessage) {
+        const state = this.getState();
+        if (sessionKeyHash) {
+            state.setCallSessionKeyHash(sessionKeyHash);
+        }
+        if (data?.wrappedSessionKey && message.fromUserId) {
+            WebRTC.receiveWrappedSessionKey(message.fromUserId, data.wrappedSessionKey, sessionKeyHash);
+        }
+    }
 }

frontend/src/core/calls/webrtc.ts

@@ -1,13 +1,11 @@
 import { getAuthHeaders } from "@/core/api/authApi";
-import type { IceServersResponse } from "@/core/types";
+import type { CallSignalingMessage, IceServersResponse } from "@/core/types";
 import { request } from "@/core/websocket";
-
-export interface CallSignalingMessage {
-    type: "call_offer" | "call_answer" | "call_ice_candidate" | "call_end" | "call_invite" | "call_accept" | "call_reject";
-    fromUserId: number;
-    toUserId: number;
-    data?: any;
-}
+import { wrapCallSessionKeyForRecipient, unwrapCallSessionKeyFromSender } from "./encryption";
+import { fetchUserPublicKey } from "@/core/api/dmApi";
+import { importAesGcmKey } from "@/utils/crypto/symmetric";
+import E2EEWorker from "./e2eeWorker?worker";
+import { rotateCallSessionKey, createSharedSecretAndDeriveSessionKey } from "./encryption";
 
 export interface WebRTCCall {
     peerConnection: RTCPeerConnection;
@@ -18,6 +16,12 @@ export interface WebRTCCall {
     remoteUsername: string;
     isEnding?: boolean;
     isMuted?: boolean;
+    // Insertable Streams E2EE
+    sessionKey?: Uint8Array | null;
+    sessionCryptoKey?: CryptoKey | null;
+    sessionId: string;
+    keyRotationTimer?: NodeJS.Timeout;
+    lastKeyRotation?: number;
 }
 
 // Global state
@@ -83,6 +87,7 @@ async function getIceServers(): Promise<RTCIceServer[]> {
     return defaultIceServers;
 }
 
+
 async function createPeerConnection(userId: number): Promise<RTCPeerConnection> {
     const iceServers = await getIceServers();
     
@@ -97,7 +102,10 @@ async function createPeerConnection(userId: number): Promise<RTCPeerConnection>
         isInitiator: false,
         remoteUserId: userId,
         remoteUsername: "",
-        isMuted: false
+        isMuted: false,
+        sessionKey: null,
+        sessionCryptoKey: null,
+        sessionId: crypto.randomUUID()
     };
 
     calls.set(userId, call);
@@ -197,6 +205,17 @@ export async function initiateCall(userId: number, username: string): Promise<bo
         // Add tracks to peer connection
         localStream.getTracks().forEach(track => call.peerConnection.addTrack(track, localStream));
 
+        // Enable insertable streams encryption on sender side if supported
+        try {
+            if (call.peerConnection.getSenders && call.peerConnection.getSenders().length > 0 && window.RTCRtpScriptTransform) {
+                const senders = call.peerConnection.getSenders();
+                for (const sender of senders) {
+                    if (!sender.track || sender.track.kind !== "audio") continue;
+                    // just mark; actual key set after wrap/send
+                }
+            }
+        } catch {}
+
         // Send call invite
         await sendSignalingMessage({
             type: "call_invite",
@@ -213,6 +232,133 @@ export async function initiateCall(userId: number, username: string): Promise<bo
     }
 }
 
+export async function sendCallSessionKey(userId: number, sessionKeyHash: string): Promise<void> {
+    try {
+        await sendSignalingMessage({
+            type: "call_session_key",
+            fromUserId: 0, // Will be set by server
+            toUserId: userId,
+            sessionKeyHash,
+            data: {}
+        });
+    } catch (error) {
+        console.error("Failed to send call session key:", error);
+    }
+}
+
+export async function sendWrappedCallSessionKey(userId: number, sessionKey: Uint8Array, sessionKeyHash: string): Promise<void> {
+    if (!authToken) throw new Error("No auth token available");
+    try {
+        const recipientPublicKey = await fetchUserPublicKey(userId, authToken);
+        if (!recipientPublicKey) {
+            console.warn("No recipient public key for", userId);
+            return;
+        }
+        const wrapped = await wrapCallSessionKeyForRecipient(recipientPublicKey, sessionKey);
+        await sendSignalingMessage({
+            type: "call_session_key",
+            fromUserId: 0,
+            toUserId: userId,
+            sessionKeyHash,
+            data: { wrappedSessionKey: wrapped }
+        });
+    } catch (e) {
+        console.error("Failed to send wrapped session key:", e);
+    }
+}
+
+async function applyE2EETransforms(call: WebRTCCall): Promise<void> {
+    try {
+        // @ts-ignore
+        if (!call.sessionKey || !window.RTCRtpScriptTransform) return;
+        const key = await importAesGcmKey(call.sessionKey);
+        call.sessionCryptoKey = key;
+        const receiver = call.peerConnection.getReceivers().find(r => r.track && r.track.kind === 'audio');
+        if (receiver) {
+            // @ts-ignore
+            receiver.transform = new RTCRtpScriptTransform(new E2EEWorker(), { key, mode: 'decrypt' });
+        }
+        const sender = call.peerConnection.getSenders().find(s => s.track && s.track.kind === 'audio');
+        if (sender) {
+            // @ts-ignore
+            sender.transform = new RTCRtpScriptTransform(new E2EEWorker(), { key, mode: 'encrypt' });
+        }
+    } catch {}
+}
+
+export async function setSessionKey(userId: number, keyBytes: Uint8Array): Promise<void> {
+    const call = calls.get(userId);
+    if (!call) return;
+    call.sessionKey = keyBytes;
+    call.lastKeyRotation = Date.now();
+    await applyE2EETransforms(call);
+    
+    // Start key rotation timer (rotate every 10 minutes for long calls)
+    if (call.keyRotationTimer) {
+        clearInterval(call.keyRotationTimer);
+    }
+    
+    call.keyRotationTimer = setInterval(async () => {
+        await rotateSessionKey(userId);
+    }, 10 * 60 * 1000); // 10 minutes
+}
+
+/**
+ * Rotate the session key for a call to provide forward secrecy
+ */
+async function rotateSessionKey(userId: number): Promise<void> {
+    const call = calls.get(userId);
+    if (!call || !call.sessionKey) return;
+    
+    try {
+        console.log("Rotating session key for call", userId);
+        
+        // Generate new session key
+        const currentSessionKey = {
+            key: call.sessionKey,
+            hash: "" // We'll generate a new hash
+        };
+        
+        const newSessionKey = await rotateCallSessionKey(currentSessionKey);
+        
+        // Update the call with new session key
+        call.sessionKey = newSessionKey.key;
+        call.lastKeyRotation = Date.now();
+        
+        // Reapply E2EE transforms with new key
+        await applyE2EETransforms(call);
+        
+        console.log("Session key rotated successfully for call", userId);
+    } catch (error) {
+        console.error("Failed to rotate session key:", error);
+    }
+}
+
+export async function receiveWrappedSessionKey(fromUserId: number, wrappedPayload: any, sessionKeyHash?: string): Promise<void> {
+    if (!authToken) return;
+    try {
+        const senderPublicKey = await fetchUserPublicKey(fromUserId, authToken);
+        if (!senderPublicKey) return;
+        if (!wrappedPayload || !sessionKeyHash) return;
+        
+        // First unwrap the session key from the encrypted payload (for validation)
+        await unwrapCallSessionKeyFromSender(senderPublicKey, {
+            salt: wrappedPayload.salt,
+            iv2: wrappedPayload.iv2,
+            wrapped: wrappedPayload.wrapped
+        });
+        
+        // Then derive the actual session key from the shared secret
+        const call = calls.get(fromUserId);
+        const isInitiator = call?.isInitiator ?? false;
+        const derivedSessionKey = await createSharedSecretAndDeriveSessionKey(senderPublicKey, sessionKeyHash, isInitiator);
+        
+        await setSessionKey(fromUserId, derivedSessionKey.key);
+    } catch (e) {
+        console.error("Failed to unwrap session key:", e);
+    }
+}
+
 export async function acceptCall(userId: number): Promise<boolean> {
     try {
         let call = calls.get(userId);
@@ -311,6 +457,25 @@ export async function onRemoteAccepted(userId: number): Promise<void> {
     }
 }
 
+async function createE2EETransform(sessionKey: NonNullable<WebRTCCall['sessionKey']>, peerConnection: RTCPeerConnection, sessionId?: string): Promise<void> {
+    try {
+        if (sessionKey && window.RTCRtpScriptTransform) {
+            const key = await importAesGcmKey(sessionKey);
+            const receiver = peerConnection.getReceivers().find(r => r.track && r.track.kind === 'audio');
+            if (receiver) {
+                receiver.transform = new RTCRtpScriptTransform(new E2EEWorker(), { key, mode: 'decrypt', sessionId });
+            }
+            const sender = peerConnection.getSenders().find(s => s.track && s.track.kind === 'audio');
+            if (sender) {
+                sender.transform = new RTCRtpScriptTransform(new E2EEWorker(), { key, mode: 'encrypt', sessionId });
+            }
+        }
+    } catch (error) {
+        console.error("Failed to create E2EE transform:", error);
+        throw error;
+    }
+}
+
 export async function handleCallOffer(userId: number, offer: RTCSessionDescriptionInit): Promise<void> {
     const call = calls.get(userId);
     if (!call) {
@@ -325,6 +490,9 @@ export async function handleCallOffer(userId: number, offer: RTCSessionDescripti
         const answer = await call.peerConnection.createAnswer();
         await call.peerConnection.setLocalDescription(answer);
 
+        // Attach transforms on callee side if session key set and insertable streams supported
+        await createE2EETransform(call.sessionKey!, call.peerConnection, call.sessionId);
+
         // Send answer to remote peer
         await sendSignalingMessage({
             type: "call_answer",
@@ -346,6 +514,8 @@ export async function handleCallAnswer(userId: number, answer: RTCSessionDescrip
 
     try {
         await call.peerConnection.setRemoteDescription(answer);
+        // After signaling completes, attach transforms on initiator side if supported
+        await createE2EETransform(call.sessionKey!, call.peerConnection, call.sessionId);
     } catch (error) {
         console.error("Failed to handle answer:", error);
         throw error;
@@ -449,6 +619,11 @@ export function getCall(userId: number): WebRTCCall | undefined {
 export function cleanupCall(userId: number): void {
     const call = calls.get(userId);
     if (call) {
+        // Clear key rotation timer
+        if (call.keyRotationTimer) {
+            clearInterval(call.keyRotationTimer);
+        }
+        
         // Close peer connection
         if (call.peerConnection) {
             call.peerConnection.close();

frontend/src/core/types.d.ts

@@ -442,9 +442,12 @@ export interface CallInvite extends CallSignalingData {
     timestamp: string;
 }
 
-export interface CallSignalingData {
-    type: "call_offer" | "call_answer" | "call_ice_candidate" | "call_end" | "call_invite" | "call_accept" | "call_reject";
+export type CallSignalingDataType = "call_offer" | "call_answer" | "call_ice_candidate" | "call_end" | "call_invite" | "call_accept" | "call_reject" | "call_session_key" | "call_signaling";
+
+export interface CallSignalingMessage extends WebSocketMessage {
+    type: CallSignalingDataType;
     fromUserId: number;
     toUserId: number;
-    data?: any;
+    sessionKeyHash?: string;
+    data: any;
 }

frontend/src/core/websocket.ts

@@ -6,7 +6,7 @@
  */
 
 import { API_WS_BASE_URL } from "./config";
-import type { WebSocketMessage } from "./types";
+import type { CallSignalingMessage, WebSocketMessage } from "./types";
 import { delay } from "@/utils/utils";
 import { CallSignalingHandler } from "@/core/calls/signaling";
 
@@ -109,7 +109,7 @@ async function onError() {
 
 websocket.addEventListener("message", (e) => {
     try {
-        const response: WebSocketMessage<any> = JSON.parse(e.data);
+        const response: CallSignalingMessage = JSON.parse(e.data);
         
         // Handle call signaling messages
         if (callSignalingHandler && response.type === "call_signaling") {

frontend/src/pages/chat/css/_callWindow.scss

@@ -162,6 +162,24 @@
                 color: $color-dark-on-surface-variant;
                 font-weight: 500;
             }
+
+            .encryption-emojis {
+                display: flex;
+                justify-content: center;
+                gap: 8px;
+                margin-top: 8px;
+
+                .encryption-emoji {
+                    font-size: 20px;
+                    display: inline-block;
+                    animation: emoji-pulse 2s ease-in-out infinite;
+                    
+                    &:nth-child(1) { animation-delay: 0s; }
+                    &:nth-child(2) { animation-delay: 0.2s; }
+                    &:nth-child(3) { animation-delay: 0.4s; }
+                    &:nth-child(4) { animation-delay: 0.6s; }
+                }
+            }
         }
     }
 }
@@ -376,3 +394,14 @@
         left: 100%;
     }
 }
+
+@keyframes emoji-pulse {
+    0%, 100% {
+        transform: scale(1);
+        opacity: 0.8;
+    }
+    50% {
+        transform: scale(1.2);
+        opacity: 1;
+    }
+}

frontend/src/pages/chat/hooks/useAudioCall.ts

@@ -1,14 +1,15 @@
-import { useAppState } from "../state";
+import { useAppState } from "@/pages/chat/state";
 import * as WebRTC from "@/core/calls/webrtc";
 import { CallSignalingHandler } from "@/core/calls/signaling";
 import { setCallSignalingHandler } from "@/core/websocket";
+import { generateCallSessionKey, generateCallEmojis, createCallSessionKeyFromHash } from "@/core/calls/encryption";
 import { createRef, useEffect } from "react";
 
 // Global audio ref shared across all instances
 let globalRemoteAudioRef = createRef<HTMLAudioElement>();
 
 export default function useAudioCall() {
-    const { chat, startCall, endCall, setCallStatus, toggleMute, user } = useAppState();
+    const { chat, startCall, endCall, setCallStatus, toggleMute, setCallEncryption, setCallSessionKeyHash, user } = useAppState();
     const remoteAudioRef = globalRemoteAudioRef;
 
     useEffect(() => {
@@ -23,7 +24,8 @@ export default function useAudioCall() {
                 const state = useAppState.getState();
                 state.receiveCall(userId, username);
             }, 
-            endCall 
+            endCall,
+            setCallSessionKeyHash
         }));
         setCallSignalingHandler(signalingHandler);
 
@@ -85,6 +87,14 @@ export default function useAudioCall() {
         };
     }, [user.authToken, chat.call.remoteUserId, setCallStatus, endCall, startCall]);
 
+    // Watch for session key hash changes and generate emojis
+    useEffect(() => {
+        if (chat.call.sessionKeyHash && chat.call.encryptionEmojis.length === 0) {
+            const emojis = generateCallEmojis(chat.call.sessionKeyHash);
+            setCallEncryption(chat.call.sessionKeyHash, emojis);
+        }
+    }, [chat.call.sessionKeyHash, chat.call.encryptionEmojis.length, setCallEncryption]);
+
     async function requestAudioPermissions(): Promise<boolean> {
         try {
             const stream = await navigator.mediaDevices.getUserMedia({ 
@@ -110,14 +120,31 @@ export default function useAudioCall() {
         }
 
 
+        let sessionKey;
+        try {
+            // Generate call session key and emojis
+            sessionKey = await generateCallSessionKey();
+            const emojis = generateCallEmojis(sessionKey.hash);
+            
             // Start the call in state
             startCall(userId, username);
             setCallStatus("calling");
+            setCallEncryption(sessionKey.hash, emojis);
+        } catch (error) {
+            console.error("Failed to generate call encryption:", error);
+            endCall();
+            return;
+        }
 
         // Initiate WebRTC call
         const success = await WebRTC.initiateCall(userId, username);
         
-        if (!success) {
+        if (success && sessionKey) {
+            // Send session key hash to the receiver for visual verification
+            await WebRTC.sendCallSessionKey(userId, sessionKey.hash);
+            // Also wrap and send the actual session key for E2EE media
+            await WebRTC.sendWrappedCallSessionKey(userId, sessionKey.key, sessionKey.hash);
+        } else {
             endCall();
         }
     };
@@ -162,6 +189,7 @@ export default function useAudioCall() {
     };
 
     async function handleIncomingCall(userId: number, username: string) {
+        // Don't generate session key here - wait for it from the caller
         await WebRTC.handleIncomingCall(userId, username);
     };
 
@@ -177,6 +205,17 @@ export default function useAudioCall() {
         await WebRTC.handleIceCandidate(userId, candidate);
     };
 
+    async function handleCallSessionKey(sessionKeyHash: string) {
+        try {
+            // Create session key from the hash provided by the caller
+            const sessionKey = await createCallSessionKeyFromHash(sessionKeyHash);
+            const emojis = generateCallEmojis(sessionKey.hash);
+            setCallEncryption(sessionKey.hash, emojis);
+        } catch (error) {
+            console.error("Failed to create call session key from hash:", error);
+        }
+    };
+
     return {
         call: chat.call,
         initiateCall,
@@ -188,6 +227,7 @@ export default function useAudioCall() {
         handleCallOffer,
         handleCallAnswer,
         handleIceCandidate,
+        handleCallSessionKey,
         remoteAudioRef
     };
 }

frontend/src/pages/chat/state.ts

@@ -29,6 +29,8 @@ interface CallState {
     remoteUsername: string | null;
     isInitiator: boolean;
     isMinimized: boolean;
+    sessionKeyHash: string | null;
+    encryptionEmojis: string[];
 }
 
 interface ChatState {
@@ -75,6 +77,8 @@ interface AppState {
     toggleMute: () => void;
     toggleCallMinimize: () => void;
     receiveCall: (userId: number, username: string) => void;
+    setCallEncryption: (sessionKeyHash: string, encryptionEmojis: string[]) => void;
+    setCallSessionKeyHash: (sessionKeyHash: string) => void;
     
     // User state
     user: UserState;
@@ -110,7 +114,9 @@ export const useAppState = create<AppState>((set, get) => ({
             remoteUserId: null,
             remoteUsername: null,
             isInitiator: false,
-            isMinimized: false
+            isMinimized: false,
+            sessionKeyHash: null,
+            encryptionEmojis: []
         }
     },
     addMessage: (message: Message) => set((state) => {
@@ -404,7 +410,9 @@ export const useAppState = create<AppState>((set, get) => ({
                 remoteUserId: userId,
                 remoteUsername: username,
                 isInitiator: true,
-                isMinimized: false
+                isMinimized: false,
+                sessionKeyHash: null,
+                encryptionEmojis: []
             }
         }
     })),
@@ -420,7 +428,9 @@ export const useAppState = create<AppState>((set, get) => ({
                 remoteUserId: null,
                 remoteUsername: null,
                 isInitiator: false,
-                isMinimized: false
+                isMinimized: false,
+                sessionKeyHash: null,
+                encryptionEmojis: []
             }
         }
     })),
@@ -467,7 +477,30 @@ export const useAppState = create<AppState>((set, get) => ({
                 remoteUserId: userId,
                 remoteUsername: username,
                 isInitiator: false,
-                isMinimized: false
+                isMinimized: false,
+                sessionKeyHash: null,
+                encryptionEmojis: []
+            }
+        }
+    })),
+    
+    setCallEncryption: (sessionKeyHash: string, encryptionEmojis: string[]) => set((state) => ({
+        chat: {
+            ...state.chat,
+            call: {
+                ...state.chat.call,
+                sessionKeyHash,
+                encryptionEmojis
+            }
+        }
+    })),
+    
+    setCallSessionKeyHash: (sessionKeyHash: string) => set((state) => ({
+        chat: {
+            ...state.chat,
+            call: {
+                ...state.chat.call,
+                sessionKeyHash
             }
         }
     }))