Working one-time message encryption and decryption

backend/models.py

@@ -76,10 +76,23 @@ class SignalPreKeyBundle(Base):
 
     id = Column(Integer, primary_key=True, index=True)
     user_id = Column(Integer, ForeignKey("user.id"), nullable=False, unique=True)
-    bundle_json = Column(Text, nullable=False)  # JSON string of PreKeyBundleData
+    bundle_json = Column(Text, nullable=False)  # JSON string of PreKeyBundleData (identity, signed prekey, registration ID)
     updated_at = Column(DateTime, default=datetime.now, onupdate=datetime.now)
 
 
+class SignalPreKey(Base):
+    __tablename__ = "signal_prekey"
+
+    id = Column(Integer, primary_key=True, index=True)
+    user_id = Column(Integer, ForeignKey("user.id"), nullable=False, index=True)
+    prekey_id = Column(Integer, nullable=False)  # The prekey ID from the client
+    public_key = Column(Text, nullable=False)  # Base64 encoded public key
+    used = Column(Boolean, default=False, nullable=False, index=True)  # Whether this prekey has been used
+    created_at = Column(DateTime, default=datetime.now)
+    
+    __table_args__ = (UniqueConstraint('user_id', 'prekey_id', name='_user_prekey_uc'),)
+
+
 class DMEnvelope(Base):
     __tablename__ = "dm_envelope"
 

backend/routes/account.py

@@ -488,7 +488,7 @@ def upload_prekey_bundle(
     db: Session = Depends(get_db)
 ):
     """Upload Signal Protocol prekey bundle for the current user"""
-    from models import SignalPreKeyBundle
+    from models import SignalPreKeyBundle, SignalPreKey
     import json
     
     bundle = payload.get("bundle")
@@ -508,11 +508,17 @@ def upload_prekey_bundle(
     if not isinstance(bundle["signedPreKey"], dict) or "keyId" not in bundle["signedPreKey"]:
         raise HTTPException(status_code=400, detail="Invalid signedPreKey format")
     
-    # Store as JSON string
+    # Store bundle (identity key, signed prekey, registration ID) - without the one-time prekey
-    bundle_json = json.dumps(bundle)
+    bundle_without_prekey = {
+        "registrationId": bundle["registrationId"],
+        "identityKey": bundle["identityKey"],
+        "signedPreKey": bundle["signedPreKey"]
+    }
+    bundle_json = json.dumps(bundle_without_prekey)
     if len(bundle_json) > 50000:  # 50KB limit
         raise HTTPException(status_code=400, detail="Bundle too large")
     
+    # Store or update the bundle
     row = db.query(SignalPreKeyBundle).filter(SignalPreKeyBundle.user_id == current_user.id).first()
     if row:
         row.bundle_json = bundle_json
@@ -520,11 +526,121 @@ def upload_prekey_bundle(
     else:
         row = SignalPreKeyBundle(user_id=current_user.id, bundle_json=bundle_json)
         db.add(row)
+    
+    # Store the one-time prekey if provided
+    if "preKey" in bundle and bundle["preKey"]:
+        prekey = bundle["preKey"]
+        if isinstance(prekey, dict) and "keyId" in prekey and "publicKey" in prekey:
+            # Check if this prekey already exists
+            existing = db.query(SignalPreKey).filter(
+                SignalPreKey.user_id == current_user.id,
+                SignalPreKey.prekey_id == prekey["keyId"]
+            ).first()
+            
+            if existing:
+                # Update existing prekey (mark as unused if it was used)
+                existing.public_key = prekey["publicKey"]
+                existing.used = False
+                existing.created_at = datetime.now()
+            else:
+                # Add new prekey
+                new_prekey = SignalPreKey(
+                    user_id=current_user.id,
+                    prekey_id=prekey["keyId"],
+                    public_key=prekey["publicKey"],
+                    used=False
+                )
+                db.add(new_prekey)
+    
     db.commit()
     
     return {"status": "ok"}
 
 
+@router.post("/crypto/signal/prekeys/bulk")
+@rate_limit_per_ip("10/minute")
+def upload_prekeys_bulk(
+    request: Request,
+    payload: dict,
+    current_user: User = Depends(get_current_user),
+    db: Session = Depends(get_db)
+):
+    """Upload multiple Signal Protocol prekeys in one request"""
+    from models import SignalPreKeyBundle, SignalPreKey
+    import json
+    
+    base_bundle = payload.get("baseBundle")
+    prekeys = payload.get("prekeys", [])
+    
+    if not base_bundle:
+        raise HTTPException(status_code=400, detail="baseBundle required")
+    
+    if not isinstance(prekeys, list):
+        raise HTTPException(status_code=400, detail="prekeys must be an array")
+    
+    # Validate base bundle structure
+    if not isinstance(base_bundle, dict):
+        raise HTTPException(status_code=400, detail="baseBundle must be a JSON object")
+    
+    # Validate required fields
+    required_fields = ["registrationId", "identityKey", "signedPreKey"]
+    for field in required_fields:
+        if field not in base_bundle:
+            raise HTTPException(status_code=400, detail=f"Missing required field in baseBundle: {field}")
+    
+    if not isinstance(base_bundle["signedPreKey"], dict) or "keyId" not in base_bundle["signedPreKey"]:
+        raise HTTPException(status_code=400, detail="Invalid signedPreKey format")
+    
+    # Store or update the base bundle (identity key, signed prekey, registration ID)
+    bundle_without_prekey = {
+        "registrationId": base_bundle["registrationId"],
+        "identityKey": base_bundle["identityKey"],
+        "signedPreKey": base_bundle["signedPreKey"]
+    }
+    bundle_json = json.dumps(bundle_without_prekey)
+    if len(bundle_json) > 50000:  # 50KB limit
+        raise HTTPException(status_code=400, detail="Bundle too large")
+    
+    # Store or update the bundle
+    row = db.query(SignalPreKeyBundle).filter(SignalPreKeyBundle.user_id == current_user.id).first()
+    if row:
+        row.bundle_json = bundle_json
+        row.updated_at = datetime.now()
+    else:
+        row = SignalPreKeyBundle(user_id=current_user.id, bundle_json=bundle_json)
+        db.add(row)
+    
+    # Store all prekeys
+    for prekey in prekeys:
+        if not isinstance(prekey, dict) or "keyId" not in prekey or "publicKey" not in prekey:
+            continue  # Skip invalid prekeys
+        
+        # Check if this prekey already exists
+        existing = db.query(SignalPreKey).filter(
+            SignalPreKey.user_id == current_user.id,
+            SignalPreKey.prekey_id == prekey["keyId"]
+        ).first()
+        
+        if existing:
+            # Update existing prekey (mark as unused if it was used)
+            existing.public_key = prekey["publicKey"]
+            existing.used = False
+            existing.created_at = datetime.now()
+        else:
+            # Add new prekey
+            new_prekey = SignalPreKey(
+                user_id=current_user.id,
+                prekey_id=prekey["keyId"],
+                public_key=prekey["publicKey"],
+                used=False
+            )
+            db.add(new_prekey)
+    
+    db.commit()
+    
+    return {"status": "ok", "uploaded": len(prekeys)}
+
+
 @router.get("/crypto/signal/prekey-bundle")
 def get_prekey_bundle(
     current_user: User = Depends(get_current_user),
@@ -553,16 +669,39 @@ def get_prekey_bundle_of(
     current_user: User = Depends(get_current_user),
     db: Session = Depends(get_db)
 ):
-    """Get Signal Protocol prekey bundle for another user"""
+    """Get Signal Protocol prekey bundle for another user with prekey rotation"""
-    from models import SignalPreKeyBundle
+    from models import SignalPreKeyBundle, SignalPreKey
     import json
     
+    # Get the base bundle (identity key, signed prekey, registration ID)
     row = db.query(SignalPreKeyBundle).filter(SignalPreKeyBundle.user_id == user_id).first()
     if not row:
         raise HTTPException(status_code=404, detail="Prekey bundle not found")
     
     try:
         bundle = json.loads(row.bundle_json)
+        
+        # Find an unused prekey for this user
+        unused_prekey = db.query(SignalPreKey).filter(
+            SignalPreKey.user_id == user_id,
+            SignalPreKey.used == False
+        ).order_by(SignalPreKey.created_at.asc()).first()
+        
+        if unused_prekey:
+            # Mark this prekey as used (atomic operation)
+            unused_prekey.used = True
+            db.commit()
+            
+            # Add the prekey to the bundle
+            bundle["preKey"] = {
+                "keyId": unused_prekey.prekey_id,
+                "publicKey": unused_prekey.public_key
+            }
+        else:
+            # No unused prekeys available - return bundle without prekey
+            # The client will need to establish a session using the signed prekey only
+            pass
+        
         return {"bundle": bundle}
     except json.JSONDecodeError:
         raise HTTPException(status_code=500, detail="Invalid bundle data")

frontend/src/core/api/chats/dm.ts

@@ -1,28 +1,139 @@
 import { API_BASE_URL } from "@/core/config";
-import { getAuthHeaders } from "../user/auth";
+import api from "@/core/api";
-import { ecdhSharedSecret, deriveWrappingKey } from "@/utils/crypto/asymmetric";
+import { importAesGcmKey, aesGcmEncrypt } from "@/utils/crypto/symmetric";
-import { importAesGcmKey, aesGcmEncrypt, aesGcmDecrypt } from "@/utils/crypto/symmetric";
 import { randomBytes } from "@/utils/crypto/kdf";
-import { getCurrentKeys } from "../user/auth";
 import { request } from "@/core/websocket";
 import type { SendDMRequest, DmEnvelope, DMEditRequest, DmEncryptedJSON, BaseDmEnvelope, User } from "@/core/types";
-import { b64, ub64 } from "@/utils/utils";
+import { b64 } from "@/utils/utils";
-import { fetchUserPublicKey } from "../crypto/identity";
+import { SignalProtocolService } from "@/utils/crypto/signalProtocol";
-import { fetchUsers, searchUsers } from "../user/search";
+import { useUserStore } from "@/state/user";
+import { addPadding, removePadding } from "@/utils/crypto/obfuscation";
 
-export async function decrypt(envelope: DmEnvelope, senderPublicKeyB64: string): Promise<string> {
+export async function decrypt(envelope: DmEnvelope, senderId: number): Promise<string> {
-    const keys = getCurrentKeys();
+    const user = useUserStore.getState().user.currentUser;
-    if (!keys) throw new Error("Keys not initialized");
+    if (!user?.id) {
+        throw new Error("User not authenticated");
+    }
 
-    // Obtain the key
+    if (!envelope.ciphertext) {
-    const shared = ecdhSharedSecret(keys.privateKey, ub64(senderPublicKeyB64));
+        throw new Error("DM envelope missing ciphertext");
-    const wkRaw = await deriveWrappingKey(shared, ub64(envelope.salt), new Uint8Array([1]));
+    }
-    const wk = await importAesGcmKey(wkRaw);
-    const mk = await aesGcmDecrypt(wk, ub64(envelope.iv2), ub64(envelope.wrappedMk));
 
-    // Decrypt
+    const signalService = new SignalProtocolService(user.id.toString());
-    const msg = await aesGcmDecrypt(await importAesGcmKey(mk), ub64(envelope.iv), ub64(envelope.ciphertext));
+    
-    return new TextDecoder().decode(msg);
+    // Remove padding (backward compatible with old messages)
+    // Check if ciphertext is base64 (padded) or already JSON (unpadded)
+    let ciphertextStr: string = envelope.ciphertext;
+    
+    // Check if it's base64 (padded messages are base64)
+    const base64Pattern = /^[A-Za-z0-9+/]*={0,2}$/;
+    const isBase64 = base64Pattern.test(envelope.ciphertext) && envelope.ciphertext.length > 0;
+    
+    if (isBase64) {
+        // Try to remove padding
+        try {
+            const unpadded = removePadding(envelope.ciphertext);
+            // Verify it's valid JSON before using it
+            JSON.parse(unpadded);
+            ciphertextStr = unpadded;
+        } catch {
+            // If padding removal fails, try using the base64 directly as JSON (shouldn't happen, but handle gracefully)
+            try {
+                JSON.parse(envelope.ciphertext);
+                ciphertextStr = envelope.ciphertext;
+            } catch {
+                // If both fail, throw an error
+                throw new Error(`Failed to process ciphertext: not valid base64 padded data and not valid JSON. Length: ${envelope.ciphertext.length}`);
+            }
+        }
+    } else {
+        // Not base64, assume it's already JSON (unpadded message)
+        ciphertextStr = envelope.ciphertext;
+    }
+    
+    // Parse Signal Protocol message
+    let signalCiphertext: { type: number; body: string };
+    try {
+        signalCiphertext = JSON.parse(ciphertextStr);
+    } catch (error) {
+        throw new Error(`Failed to parse ciphertext as JSON: ${error instanceof Error ? error.message : String(error)}. Ciphertext length: ${ciphertextStr.length}, first 100 chars: ${ciphertextStr.substring(0, 100)}`);
+    }
+    
+    if (!signalCiphertext || typeof signalCiphertext !== "object") {
+        throw new Error("Invalid Signal Protocol message format: not an object");
+    }
+    
+    if (typeof signalCiphertext.type !== "number") {
+        throw new Error("Invalid Signal Protocol message format: type is not a number");
+    }
+    
+    if (!signalCiphertext.body || typeof signalCiphertext.body !== "string") {
+        throw new Error("Invalid Signal Protocol message format: body is missing or not a string");
+    }
+    
+    // Check if body contains non-printable characters (corrupted binary data from old encryption)
+    // This must be checked first, before any base64 validation
+    const hasNonPrintable = /[\x00-\x08\x0B-\x0C\x0E-\x1F\x7F-\x9F]/.test(signalCiphertext.body);
+    if (hasNonPrintable) {
+        // This is a corrupted message from before the base64 conversion fix
+        // It cannot be decrypted - the body contains raw binary data instead of base64
+        console.warn(`Message corrupted: body contains binary data instead of base64 (envelope ID: ${envelope.id}). This message was encrypted before the encryption fix and cannot be decrypted.`);
+        return "_This message is corrupted and cannot be displayed._";
+    }
+    
+    // Check if body contains Unicode escape sequences (from JSON.stringify escaping)
+    // If so, we need to unescape them to get the actual base64 string
+    let bodyToDecode = signalCiphertext.body;
+    
+    // Check for literal backslash-u sequences (before JSON parsing, these would be "\\u")
+    // After JSON parsing, Unicode escapes are converted to actual characters, so we check for
+    // the pattern that indicates it might have been escaped
+    if (bodyToDecode.includes("\\u") || bodyToDecode.match(/\\u[0-9a-fA-F]{4}/)) {
+        // Try to unescape Unicode sequences by wrapping in JSON quotes
+        try {
+            bodyToDecode = JSON.parse(`"${bodyToDecode.replace(/\\/g, "\\\\")}"`);
+        } catch {
+            // If unescaping fails, use the original
+            bodyToDecode = signalCiphertext.body;
+        }
+    }
+    
+    // Validate that body is valid base64 before attempting decryption
+    // Check if it's a valid base64 string (only contains base64 characters and padding)
+    const base64Regex = /^[A-Za-z0-9+/]*={0,2}$/;
+    if (!base64Regex.test(bodyToDecode)) {
+        // Log for debugging - this should help identify the issue
+        console.error("Invalid base64 in body:", {
+            bodyType: typeof signalCiphertext.body,
+            bodyLength: signalCiphertext.body.length,
+            unescapedLength: bodyToDecode.length,
+            first50: signalCiphertext.body.substring(0, 50),
+            unescapedFirst50: bodyToDecode.substring(0, 50),
+            envelopeId: envelope.id
+        });
+        throw new Error(`Invalid base64 format in ciphertext body`);
+    }
+    
+    // Use the unescaped body for decryption
+    signalCiphertext.body = bodyToDecode;
+    
+    try {
+        // Try to decode a small portion to validate base64
+        atob(signalCiphertext.body.substring(0, Math.min(4, signalCiphertext.body.length)));
+    } catch (error) {
+        // Log for debugging
+        console.error("Base64 decode failed:", {
+            bodyLength: signalCiphertext.body.length,
+            first50: signalCiphertext.body.substring(0, 50),
+            last50: signalCiphertext.body.substring(Math.max(0, signalCiphertext.body.length - 50)),
+            envelopeId: envelope.id,
+            error: error instanceof Error ? error.message : String(error)
+        });
+        throw new Error(`Invalid base64 in ciphertext body: ${error instanceof Error ? error.message : String(error)}`);
+    }
+    
+    const plaintext = await signalService.decryptMessage(senderId, signalCiphertext);
+    return plaintext;
 }
 
 export async function fetchMessages(userId: number, token: string, limit: number = 50, beforeId?: number): Promise<{ messages: DmEnvelope[]; has_more: boolean }> {
@@ -31,35 +142,86 @@ export async function fetchMessages(userId: number, token: string, limit: number
         url += `&before_id=${beforeId}`;
     }
     const response = await globalThis.fetch(url, {
-        headers: getAuthHeaders(token, true)
+        headers: api.user.auth.getAuthHeaders(token, true)
     });
     if (!response.ok) return { messages: [], has_more: false };
     const data = await response.json();
     return { messages: data.messages || [], has_more: data.has_more ?? false };
 }
 
-export async function send(recipientId: number, recipientPublicKeyB64: string, plaintext: string, authToken: string, replyToId?: number): Promise<void> {
+export async function send(recipientId: number, plaintext: string, authToken: string, replyToId?: number): Promise<void> {
-    const keys = getCurrentKeys();
+    const user = useUserStore.getState().user.currentUser;
-    if (!keys) throw new Error("Keys not initialized");
+    if (!user?.id) {
+        throw new Error("User not authenticated");
+    }
 
-    // Encryption key
+    const signalService = new SignalProtocolService(user.id.toString());
-    const mk = randomBytes(32);
-    const wkSalt = randomBytes(16);
-    const shared = ecdhSharedSecret(keys.privateKey, ub64(recipientPublicKeyB64));
-    const wkRaw = await deriveWrappingKey(shared, wkSalt, new Uint8Array([1]));
-    const wk = await importAesGcmKey(wkRaw);
     
-    // Encrypt the message
+    // Check if we have a session, if not, fetch prekey bundle and establish one
-    const encMsg = await aesGcmEncrypt(await importAesGcmKey(mk), new TextEncoder().encode(plaintext));
+    const hasSession = await signalService.hasSession(recipientId);
-    const wrap = await aesGcmEncrypt(wk, mk);
+    if (!hasSession) {
+        try {
+            const bundle = await api.crypto.prekeys.fetchPreKeyBundle(recipientId, authToken);
+            await signalService.processPreKeyBundle(recipientId, bundle);
+        } catch (error) {
+            // Re-throw PrekeyExhaustedError as-is for proper handling
+            if (error instanceof api.crypto.prekeys.PrekeyExhaustedError) {
+                throw error;
+            }
+            // Re-throw other errors
+            throw error;
+        }
+    }
+    
+    // Encrypt with Signal Protocol
+    const ciphertext = await signalService.encryptMessage(recipientId, plaintext);
+    
+    // Verify the body is valid base64 before stringifying
+    if (ciphertext.body && typeof ciphertext.body === "string") {
+        try {
+            // Test that body is valid base64
+            atob(ciphertext.body.substring(0, Math.min(4, ciphertext.body.length)));
+            
+            // Verify the entire body is valid base64
+            const base64Regex = /^[A-Za-z0-9+/]*={0,2}$/;
+            if (!base64Regex.test(ciphertext.body)) {
+                console.error("Invalid base64 characters in encrypted body:", {
+                    bodyLength: ciphertext.body.length,
+                    first100: ciphertext.body.substring(0, 100),
+                    last100: ciphertext.body.substring(Math.max(0, ciphertext.body.length - 100))
+                });
+                throw new Error("Encrypted body contains invalid base64 characters");
+            }
+        } catch (error) {
+            throw new Error(`Encrypted body is not valid base64: ${error instanceof Error ? error.message : String(error)}`);
+        }
+    }
+    
+    // Stringify the ciphertext - JSON.stringify should not escape base64 strings
+    const ciphertextJson = JSON.stringify(ciphertext);
+    
+    // Verify the stringified JSON doesn't have escaped characters in the body field
+    const parsed = JSON.parse(ciphertextJson);
+    if (parsed.body !== ciphertext.body) {
+        console.error("Body was modified during JSON stringification:", {
+            original: ciphertext.body.substring(0, 50),
+            stringified: parsed.body.substring(0, 50),
+            originalLength: ciphertext.body.length,
+            stringifiedLength: parsed.body.length
+        });
+        throw new Error("Body was incorrectly escaped during JSON stringification");
+    }
+    
+    // Add padding to obfuscate message size (anti-censorship)
+    const paddedCiphertext = addPadding(ciphertextJson);
     
     const payload: SendDMRequest = {
         recipientId: recipientId,
-        iv: b64(encMsg.iv),
+        iv: "", // Not used for Signal Protocol
-        ciphertext: b64(encMsg.ciphertext),
+        ciphertext: paddedCiphertext, // Padded Signal Protocol message
-        salt: b64(wkSalt),
+        salt: "", // Not used for Signal Protocol
-        iv2: b64(wrap.iv),
+        iv2: "", // Not used for Signal Protocol
-        wrappedMk: b64(wrap.ciphertext)
+        wrappedMk: "" // Not used for Signal Protocol
     };
     if (replyToId) payload.replyToId = replyToId;
 
@@ -73,17 +235,39 @@ export async function send(recipientId: number, recipientPublicKeyB64: string, p
     });
 }
 
-export async function sendWithFiles(recipientId: number, recipientPublicKeyB64: string, plaintextJson: string, files: File[], token: string): Promise<void> {
+export async function sendWithFiles(recipientId: number, plaintextJson: string, files: File[], token: string): Promise<void> {
-    const keys = getCurrentKeys();
+    const user = useUserStore.getState().user.currentUser;
-    if (!keys) throw new Error("Keys not initialized");
+    if (!user?.id) {
+        throw new Error("User not authenticated");
+    }
 
+    const signalService = new SignalProtocolService(user.id.toString());
+    
+    // Check if we have a session, if not, fetch prekey bundle and establish one
+    const hasSession = await signalService.hasSession(recipientId);
+    if (!hasSession) {
+        try {
+            const bundle = await api.crypto.prekeys.fetchPreKeyBundle(recipientId, token);
+            await signalService.processPreKeyBundle(recipientId, bundle);
+        } catch (error) {
+            // Re-throw PrekeyExhaustedError as-is for proper handling
+            if (error instanceof api.crypto.prekeys.PrekeyExhaustedError) {
+                throw error;
+            }
+            // Re-throw other errors
+            throw error;
+        }
+    }
+
+    // Generate master key for file encryption
     const mk = randomBytes(32);
-    const wkSalt = randomBytes(16);
-    const shared = await ecdhSharedSecret(keys.privateKey, ub64(recipientPublicKeyB64));
-    const wkRaw = await deriveWrappingKey(shared, wkSalt, new Uint8Array([1]));
-    const wk = await importAesGcmKey(wkRaw);
     
-    const wrap = await aesGcmEncrypt(wk, mk);
+    // Encrypt the master key using Signal Protocol
+    const mkBase64 = b64(mk);
+    const encryptedMk = await signalService.encryptMessage(recipientId, mkBase64);
+    
+    // Add padding to obfuscate master key size
+    const paddedMk = addPadding(JSON.stringify(encryptedMk));
 
     const form = new FormData();
     const names: string[] = [];
@@ -115,30 +299,54 @@ export async function sendWithFiles(recipientId: number, recipientPublicKeyB64:
         recipientId: recipientId,
         iv: b64(encMsg.iv),
         ciphertext: b64(encMsg.ciphertext),
-        salt: b64(wkSalt),
+        salt: "", // Not used for Signal Protocol
-        iv2: b64(wrap.iv),
+        iv2: "", // Not used for Signal Protocol
-        wrappedMk: b64(wrap.ciphertext)
+        wrappedMk: paddedMk // Padded Signal Protocol encrypted master key
     } satisfies BaseDmEnvelope));
 
     await globalThis.fetch(`${API_BASE_URL}/dm/send`, {
         method: "POST",
-        headers: getAuthHeaders(token, false),
+        headers: api.user.auth.getAuthHeaders(token, false),
         body: form
     });
 }
 
-export async function edit(id: number, recipientPublicKeyB64: string, newPlaintextJson: string, authToken: string): Promise<void> {
+export async function edit(id: number, recipientId: number, newPlaintextJson: string, authToken: string): Promise<void> {
-    const keys = getCurrentKeys();
+    const user = useUserStore.getState().user.currentUser;
-    if (!keys) throw new Error("Keys not initialized");
+    if (!user?.id) {
+        throw new Error("User not authenticated");
+    }
 
-    // We cannot reuse the old mk safely without knowing it; generate a fresh mk and wrap
+    const signalService = new SignalProtocolService(user.id.toString());
+    
+    // Check if we have a session, if not, fetch prekey bundle and establish one
+    const hasSession = await signalService.hasSession(recipientId);
+    if (!hasSession) {
+        try {
+            const bundle = await api.crypto.prekeys.fetchPreKeyBundle(recipientId, authToken);
+            await signalService.processPreKeyBundle(recipientId, bundle);
+        } catch (error) {
+            // Re-throw PrekeyExhaustedError as-is for proper handling
+            if (error instanceof api.crypto.prekeys.PrekeyExhaustedError) {
+                throw error;
+            }
+            // Re-throw other errors
+            throw error;
+        }
+    }
+
+    // Generate fresh master key for the edited message
     const mk = randomBytes(32);
-    const wkSalt = randomBytes(16);
+    
-    const shared = await ecdhSharedSecret(keys.privateKey, ub64(recipientPublicKeyB64));
+    // Encrypt the master key using Signal Protocol
-    const wkRaw = await deriveWrappingKey(shared, wkSalt, new Uint8Array([1]));
+    const mkBase64 = b64(mk);
-    const wk = await importAesGcmKey(wkRaw);
+    const encryptedMk = await signalService.encryptMessage(recipientId, mkBase64);
+    
+    // Add padding to obfuscate master key size
+    const paddedMk = addPadding(JSON.stringify(encryptedMk));
+    
+    // Encrypt the message content with the master key
     const encMsg = await aesGcmEncrypt(await importAesGcmKey(mk), new TextEncoder().encode(newPlaintextJson));
-    const wrap = await aesGcmEncrypt(wk, mk);
 
     await request({
         type: "dmEdit",
@@ -147,9 +355,9 @@ export async function edit(id: number, recipientPublicKeyB64: string, newPlainte
             id,
             iv: b64(encMsg.iv),
             ciphertext: b64(encMsg.ciphertext),
-            iv2: b64(wrap.iv),
+            iv2: "", // Not used for Signal Protocol
-            wrappedMk: b64(wrap.ciphertext),
+            wrappedMk: paddedMk, // Padded Signal Protocol encrypted master key
-            salt: b64(wkSalt)
+            salt: "" // Not used for Signal Protocol
         }
     } as DMEditRequest);
 }
@@ -170,7 +378,7 @@ export interface ConversationResponse {
 
 export async function conversations(token: string): Promise<ConversationResponse[]> {
     const res = await fetch(`${API_BASE_URL}/dm/conversations`, {
-        headers: getAuthHeaders(token, true)
+        headers: api.user.auth.getAuthHeaders(token, true)
     });
     if (!res.ok) return [];
     const data = await res.json();
@@ -189,6 +397,7 @@ export async function markRead(id: number, authToken: string): Promise<void> {
 }
 
 // Re-export user functions for convenience
-export { fetchUsers, searchUsers, fetchUserPublicKey };
+export { fetchUsers, searchUsers } from "@/core/api/users";
+export { fetchUserPublicKey } from "@/core/api/crypto/identity";
 
 

frontend/src/core/api/crypto.ts

@@ -79,15 +79,22 @@ export async function uploadBackupBlob(blobJson: string, token: string): Promise
  * Uploads Signal Protocol prekey bundle for the current user
  */
 export async function uploadPreKeyBundle(bundle: PreKeyBundleData, token: string): Promise<void> {
-    const payload = { bundle };
+    // Re-export from prekeys.ts
+    const { uploadPreKeyBundle: upload } = await import("./crypto/prekeys");
+    return upload(bundle, token);
+}
 
-    const headers = getAuthHeaders(token, true);
+/**
-    const res = await fetch(`${API_BASE_URL}/crypto/signal/prekey-bundle`, {
+ * Uploads all available prekeys to the server for rotation
-        method: "POST",
+ */
-        headers,
+export async function uploadAllPreKeys(
-        body: JSON.stringify(payload)
+    baseBundle: Omit<PreKeyBundleData, "preKey">,
-    });
+    prekeys: Array<{ keyId: number; publicKey: string }>,
-    if (!res.ok) throw new Error("Failed to upload prekey bundle");
+    token: string
+): Promise<void> {
+    // Re-export from prekeys.ts
+    const { uploadAllPreKeys: upload } = await import("./crypto/prekeys");
+    return upload(baseBundle, prekeys, token);
 }
 
 /**

frontend/src/core/api/crypto/prekeys.ts

@@ -1,14 +1,89 @@
-// Placeholder for Signal Protocol pre-key management
+import { API_BASE_URL } from "@/core/config";
-// Will be implemented when Signal Protocol is added
+import { getAuthHeaders } from "../user/auth";
+import type { PreKeyBundleData } from "@/utils/crypto/signalProtocol";
 
-export async function upload(_bundle: unknown, _token: string): Promise<void> {
+/**
-    // TODO: Implement Signal Protocol pre-key upload
+ * Uploads Signal Protocol prekey bundle for the current user
-    throw new Error("Not implemented yet");
+ * This uploads the base bundle (identity, signed prekey) and one prekey
+ */
+export async function uploadPreKeyBundle(bundle: PreKeyBundleData, token: string): Promise<void> {
+    const payload = { bundle };
+
+    const headers = getAuthHeaders(token, true);
+    const res = await fetch(`${API_BASE_URL}/crypto/signal/prekey-bundle`, {
+        method: "POST",
+        headers,
+        body: JSON.stringify(payload)
+    });
+    if (!res.ok) throw new Error("Failed to upload prekey bundle");
 }
 
-export async function fetch(_userId: number, _token: string): Promise<unknown> {
+/**
-    // TODO: Implement Signal Protocol pre-key fetch
+ * Uploads all available prekeys to the server for rotation in a single request
-    throw new Error("Not implemented yet");
+ */
+export async function uploadAllPreKeys(
+    baseBundle: Omit<PreKeyBundleData, "preKey">,
+    prekeys: Array<{ keyId: number; publicKey: string }>,
+    token: string
+): Promise<void> {
+    const headers = getAuthHeaders(token, true);
+    const payload = {
+        baseBundle,
+        prekeys
+    };
+    
+    const res = await fetch(`${API_BASE_URL}/crypto/signal/prekeys/bulk`, {
+        method: "POST",
+        headers,
+        body: JSON.stringify(payload)
+    });
+    
+    if (!res.ok) {
+        throw new Error(`Failed to upload prekeys: ${res.statusText}`);
+    }
+}
+
+/**
+ * Custom error for prekey exhaustion
+ */
+export class PrekeyExhaustedError extends Error {
+    constructor(public readonly recipientId: number) {
+        super("Recipient's encryption keys are temporarily unavailable. They need to come online to refresh their keys.");
+        this.name = "PrekeyExhaustedError";
+    }
+}
+
+/**
+ * Fetches Signal Protocol prekey bundle for another user
+ * @throws {PrekeyExhaustedError} If the recipient has no unused prekeys available
+ */
+export async function fetchPreKeyBundle(userId: number, token: string): Promise<PreKeyBundleData> {
+    const headers = getAuthHeaders(token, true);
+    const res = await fetch(`${API_BASE_URL}/crypto/signal/prekey-bundle/of/${userId}`, {
+        method: "GET",
+        headers
+    });
+    if (!res.ok) {
+        if (res.status === 404) {
+            throw new Error("Recipient has not set up encryption. They need to log in to initialize their encryption keys.");
+        }
+        throw new Error("Failed to fetch prekey bundle");
+    }
+    const data = await res.json();
+    const bundle = data.bundle;
+    
+    // Check if bundle exists but has no prekey (all prekeys exhausted)
+    if (!bundle) {
+        throw new PrekeyExhaustedError(userId);
+    }
+    
+    // If bundle exists but has no preKey field, it means all prekeys are exhausted
+    // The backend returns bundle without preKey when no unused prekeys are available
+    if (!bundle.preKey) {
+        throw new PrekeyExhaustedError(userId);
+    }
+    
+    return bundle;
 }
 
 

frontend/src/core/api/dmApi.ts

@@ -1,16 +1,13 @@
 import { API_BASE_URL } from "@/core/config";
-import { getAuthHeaders } from "./account";
+import api from "@/core/api";
 import { importAesGcmKey, aesGcmEncrypt } from "@/utils/crypto/symmetric";
 import { randomBytes } from "@/utils/crypto/kdf";
-import { getCurrentKeys } from "./account";
 import { request } from "@/core/websocket";
 import type { SendDMRequest, DmEnvelope, DMEditRequest, DmEncryptedJSON, BaseDmEnvelope, User } from "@/core/types";
-import { b64, ub64 } from "@/utils/utils";
+import { b64 } from "@/utils/utils";
-import { fetchUserPublicKey, fetchPreKeyBundle } from "./crypto";
-import { fetchUsers, searchUsers } from "./users";
 import { SignalProtocolService } from "@/utils/crypto/signalProtocol";
 import { useUserStore } from "@/state/user";
-import { ecdhSharedSecret, deriveWrappingKey } from "@/utils/crypto/asymmetric";
+import { addPadding, removePadding } from "@/utils/crypto/obfuscation";
 
 export async function decryptDm(envelope: DmEnvelope, senderId: number): Promise<string> {
     const user = useUserStore.getState().user.currentUser;
@@ -18,21 +15,110 @@ export async function decryptDm(envelope: DmEnvelope, senderId: number): Promise
         throw new Error("User not authenticated");
     }
 
-    const signalService = new SignalProtocolService(user.id.toString());
+    if (!envelope.ciphertext) {
-    
+        throw new Error("DM envelope missing ciphertext");
-    // Parse Signal Protocol message
-    const signalCiphertext = JSON.parse(envelope.ciphertext);
-    if (!signalCiphertext.type || !signalCiphertext.body) {
-        throw new Error("Invalid Signal Protocol message format");
     }
 
+    const signalService = new SignalProtocolService(user.id.toString());
+    
+    // Remove padding (backward compatible with old messages)
+    // Check if ciphertext is base64 (padded messages are base64)
+    let ciphertextStr: string = envelope.ciphertext;
+    
+    // Check if it's base64 (padded messages are base64)
+    const base64Pattern = /^[A-Za-z0-9+/]*={0,2}$/;
+    const isBase64 = base64Pattern.test(envelope.ciphertext) && envelope.ciphertext.length > 0;
+    
+    if (isBase64) {
+        // Try to remove padding
+        try {
+            const unpadded = removePadding(envelope.ciphertext);
+            // Verify it's valid JSON before using it
+            JSON.parse(unpadded);
+            ciphertextStr = unpadded;
+        } catch {
+            // If padding removal fails, try using the base64 directly as JSON (shouldn't happen, but handle gracefully)
+            try {
+                JSON.parse(envelope.ciphertext);
+                ciphertextStr = envelope.ciphertext;
+            } catch {
+                // If both fail, throw an error
+                throw new Error(`Failed to process ciphertext: not valid base64 padded data and not valid JSON. Length: ${envelope.ciphertext.length}`);
+            }
+        }
+    } else {
+        // Not base64, assume it's already JSON (unpadded message)
+        ciphertextStr = envelope.ciphertext;
+    }
+    
+    // Parse Signal Protocol message
+    let signalCiphertext: { type: number; body: string };
+    try {
+        signalCiphertext = JSON.parse(ciphertextStr);
+    } catch (error) {
+        throw new Error(`Failed to parse Signal Protocol message: ${error instanceof Error ? error.message : String(error)}`);
+    }
+    
+    if (!signalCiphertext || typeof signalCiphertext !== "object") {
+        throw new Error("Invalid Signal Protocol message format: not an object");
+    }
+    
+    if (typeof signalCiphertext.type !== "number") {
+        throw new Error("Invalid Signal Protocol message format: type is not a number");
+    }
+    
+    if (!signalCiphertext.body || typeof signalCiphertext.body !== "string") {
+        throw new Error("Invalid Signal Protocol message format: body is missing or not a string");
+    }
+    
+    // Validate that body is valid base64 before attempting decryption
+    const base64Regex = /^[A-Za-z0-9+/]*={0,2}$/;
+    if (!base64Regex.test(signalCiphertext.body)) {
+        // Check if body contains non-printable characters (corrupted binary data)
+        const hasNonPrintable = /[\x00-\x08\x0B-\x0C\x0E-\x1F\x7F-\x9F]/.test(signalCiphertext.body);
+        if (hasNonPrintable) {
+            // This is a corrupted message from before the base64 conversion fix
+            // It cannot be decrypted - the body contains raw binary data instead of base64
+            console.warn(`Message corrupted: body contains binary data instead of base64 (envelope ID: ${envelope.id}). This message was encrypted before the encryption fix and cannot be decrypted.`);
+            
+            return "_This message is corrupted and cannot be displayed._";
+        }
+        
+        console.error("Invalid base64 in body:", {
+            bodyType: typeof signalCiphertext.body,
+            bodyLength: signalCiphertext.body.length,
+            first50: signalCiphertext.body.substring(0, 50),
+            last50: signalCiphertext.body.substring(Math.max(0, signalCiphertext.body.length - 50)),
+            envelopeId: envelope.id
+        });
+        throw new Error(`Invalid base64 format in ciphertext body`);
+    }
+    
+    try {
+        // Try to decode a small portion to validate base64
+        atob(signalCiphertext.body.substring(0, Math.min(4, signalCiphertext.body.length)));
+    } catch (error) {
+        console.error("Base64 decode failed:", {
+            bodyLength: signalCiphertext.body.length,
+            first50: signalCiphertext.body.substring(0, 50),
+            last50: signalCiphertext.body.substring(Math.max(0, signalCiphertext.body.length - 50)),
+            envelopeId: envelope.id,
+            error: error instanceof Error ? error.message : String(error)
+        });
+        throw new Error(`Invalid base64 in ciphertext body: ${error instanceof Error ? error.message : String(error)}`);
+    }
+    
+    try {
         const plaintext = await signalService.decryptMessage(senderId, signalCiphertext);
         return plaintext;
+    } catch (error) {
+        throw new Error(`Failed to decrypt DM: ${error instanceof Error ? error.message : String(error)}`);
+    }
 }
 
 export async function fetchDMHistory(userId: number, token: string, limit: number = 50): Promise<DmEnvelope[]> {
     const response = await fetch(`${API_BASE_URL}/dm/history/${userId}?limit=${limit}`, {
-        headers: getAuthHeaders(token, true)
+        headers: api.user.auth.getAuthHeaders(token, true)
     });
     if (!response.ok) return [];
     const data = await response.json();
@@ -52,9 +138,9 @@ export async function sendDMViaWebSocket(recipientId: number, plaintext: string,
     const hasSession = await signalService.hasSession(recipientId);
     if (!hasSession) {
         // Fetch prekey bundle from server
-        const bundle = await fetchPreKeyBundle(recipientId, authToken);
+        const bundle = await api.crypto.prekeys.fetchPreKeyBundle(recipientId, authToken);
         if (!bundle) {
-            throw new Error("No Signal Protocol prekey bundle available for recipient");
+            throw new Error(`Recipient (user ID: ${recipientId}) has not set up encryption. They need to log in to initialize their encryption keys.`);
         }
         await signalService.processPreKeyBundle(recipientId, bundle);
     }
@@ -62,10 +148,13 @@ export async function sendDMViaWebSocket(recipientId: number, plaintext: string,
     // Encrypt with Signal Protocol
     const ciphertext = await signalService.encryptMessage(recipientId, plaintext);
     
+    // Add padding to obfuscate message size (anti-censorship)
+    const paddedCiphertext = addPadding(JSON.stringify(ciphertext));
+    
     const payload: SendDMRequest = {
         recipientId: recipientId,
         iv: "", // Not used for Signal Protocol
-        ciphertext: JSON.stringify(ciphertext), // Store Signal Protocol message as JSON
+        ciphertext: paddedCiphertext, // Padded Signal Protocol message
         salt: "", // Not used for Signal Protocol
         iv2: "", // Not used for Signal Protocol
         wrappedMk: "" // Not used for Signal Protocol
@@ -82,17 +171,33 @@ export async function sendDMViaWebSocket(recipientId: number, plaintext: string,
     });
 }
 
-export async function sendDmWithFiles(recipientId: number, recipientPublicKeyB64: string, plaintextJson: string, files: File[], token: string): Promise<void> {
+export async function sendDmWithFiles(recipientId: number, plaintextJson: string, files: File[], token: string): Promise<void> {
-    const keys = getCurrentKeys();
+    const user = useUserStore.getState().user.currentUser;
-    if (!keys) throw new Error("Keys not initialized");
+    if (!user?.id) {
+        throw new Error("User not authenticated");
+    }
 
+    const signalService = new SignalProtocolService(user.id.toString());
+    
+    // Check if we have a session, if not, fetch prekey bundle and establish one
+    const hasSession = await signalService.hasSession(recipientId);
+    if (!hasSession) {
+        const bundle = await api.crypto.prekeys.fetchPreKeyBundle(recipientId, token);
+        if (!bundle) {
+            throw new Error(`Recipient (user ID: ${recipientId}) has not set up encryption. They need to log in to initialize their encryption keys.`);
+        }
+        await signalService.processPreKeyBundle(recipientId, bundle);
+    }
+
+    // Generate master key for file encryption
     const mk = randomBytes(32);
-    const wkSalt = randomBytes(16);
-    const shared = ecdhSharedSecret(keys.privateKey, ub64(recipientPublicKeyB64));
-    const wkRaw = await deriveWrappingKey(shared, wkSalt, new Uint8Array([1]));
-    const wk = await importAesGcmKey(wkRaw);
     
-    const wrap = await aesGcmEncrypt(wk, mk);
+    // Encrypt the master key using Signal Protocol
+    const mkBase64 = b64(mk);
+    const encryptedMk = await signalService.encryptMessage(recipientId, mkBase64);
+    
+    // Add padding to obfuscate master key size
+    const paddedMk = addPadding(JSON.stringify(encryptedMk));
 
     const form = new FormData();
     const names: string[] = [];
@@ -124,30 +229,48 @@ export async function sendDmWithFiles(recipientId: number, recipientPublicKeyB64
         recipientId: recipientId,
         iv: b64(encMsg.iv),
         ciphertext: b64(encMsg.ciphertext),
-        salt: b64(wkSalt),
+        salt: "", // Not used for Signal Protocol
-        iv2: b64(wrap.iv),
+        iv2: "", // Not used for Signal Protocol
-        wrappedMk: b64(wrap.ciphertext)
+        wrappedMk: paddedMk // Padded Signal Protocol encrypted master key
     } satisfies BaseDmEnvelope));
 
     await fetch(`${API_BASE_URL}/dm/send`, {
         method: "POST",
-        headers: getAuthHeaders(token, false),
+        headers: api.user.auth.getAuthHeaders(token, false),
         body: form
     });
 }
 
-export async function editDmEnvelope(id: number, recipientPublicKeyB64: string, newPlaintextJson: string, authToken: string): Promise<void> {
+export async function editDmEnvelope(id: number, recipientId: number, newPlaintextJson: string, authToken: string): Promise<void> {
-    const keys = getCurrentKeys();
+    const user = useUserStore.getState().user.currentUser;
-    if (!keys) throw new Error("Keys not initialized");
+    if (!user?.id) {
+        throw new Error("User not authenticated");
+    }
 
-    // We cannot reuse the old mk safely without knowing it; generate a fresh mk and wrap
+    const signalService = new SignalProtocolService(user.id.toString());
+    
+    // Check if we have a session, if not, fetch prekey bundle and establish one
+    const hasSession = await signalService.hasSession(recipientId);
+    if (!hasSession) {
+        const bundle = await api.crypto.prekeys.fetchPreKeyBundle(recipientId, authToken);
+        if (!bundle) {
+            throw new Error("No Signal Protocol prekey bundle available for recipient");
+        }
+        await signalService.processPreKeyBundle(recipientId, bundle);
+    }
+
+    // Generate fresh master key for the edited message
     const mk = randomBytes(32);
-    const wkSalt = randomBytes(16);
+    
-    const shared = ecdhSharedSecret(keys.privateKey, ub64(recipientPublicKeyB64));
+    // Encrypt the master key using Signal Protocol
-    const wkRaw = await deriveWrappingKey(shared, wkSalt, new Uint8Array([1]));
+    const mkBase64 = b64(mk);
-    const wk = await importAesGcmKey(wkRaw);
+    const encryptedMk = await signalService.encryptMessage(recipientId, mkBase64);
+    
+    // Add padding to obfuscate master key size
+    const paddedMk = addPadding(JSON.stringify(encryptedMk));
+    
+    // Encrypt the message content with the master key
     const encMsg = await aesGcmEncrypt(await importAesGcmKey(mk), new TextEncoder().encode(newPlaintextJson));
-    const wrap = await aesGcmEncrypt(wk, mk);
 
     await request({
         type: "dmEdit",
@@ -156,9 +279,9 @@ export async function editDmEnvelope(id: number, recipientPublicKeyB64: string,
             id,
             iv: b64(encMsg.iv),
             ciphertext: b64(encMsg.ciphertext),
-            iv2: b64(wrap.iv),
+            iv2: "", // Not used for Signal Protocol
-            wrappedMk: b64(wrap.ciphertext),
+            wrappedMk: paddedMk, // Padded Signal Protocol encrypted master key
-            salt: b64(wkSalt)
+            salt: "" // Not used for Signal Protocol
         }
     } as DMEditRequest);
 }
@@ -178,11 +301,12 @@ export interface DMConversationResponse {
 }
 
 // Re-export for convenience
-export { fetchUsers, searchUsers, fetchUserPublicKey };
+export { fetchUsers, searchUsers } from "./users";
+export { fetchUserPublicKey } from "./crypto/identity";
 
 export async function fetchDMConversations(token: string): Promise<DMConversationResponse[]> {
     const res = await fetch(`${API_BASE_URL}/dm/conversations`, {
-        headers: getAuthHeaders(token, true)
+        headers: api.user.auth.getAuthHeaders(token, true)
     });
     if (!res.ok) return [];
     const data = await res.json();

frontend/src/core/typingManager.ts

@@ -5,7 +5,7 @@
  * @version 1.0.0
  */
 
-import { request } from "./websocket";
+import { send } from "./websocket";
 import type {
     TypingWebSocketMessage,
     StopTypingWebSocketMessage,
@@ -39,7 +39,6 @@ export class TypingManager {
     async sendTyping(): Promise<void> {
         if (!this.authToken) return;
 
-        try {
         const message: TypingRequest = {
             type: "typing",
             credentials: {
@@ -49,11 +48,9 @@ export class TypingManager {
             data: {}
         };
 
-            await request(message);
+        // Fire-and-forget - don't wait for response
+        send(message);
         this.scheduleStopTyping("public");
-        } catch (error) {
-            console.error("Failed to send typing indicator:", error);
-        }
     }
 
     /**
@@ -62,7 +59,6 @@ export class TypingManager {
     async sendStopTyping(): Promise<void> {
         if (!this.authToken) return;
 
-        try {
         const message: StopTypingRequest = {
             type: "stopTyping",
             credentials: {
@@ -72,11 +68,9 @@ export class TypingManager {
             data: {}
         };
 
-            await request(message);
+        // Fire-and-forget - don't wait for response
+        send(message);
         this.clearStopTypingTimeout("public");
-        } catch (error) {
-            console.error("Failed to send stop typing indicator:", error);
-        }
     }
 
     /**
@@ -85,7 +79,6 @@ export class TypingManager {
     async sendDmTyping(recipientId: number): Promise<void> {
         if (!this.authToken) return;
 
-        try {
         const message: DmTypingRequest = {
             type: "dmTyping",
             credentials: {
@@ -97,11 +90,9 @@ export class TypingManager {
             }
         };
 
-            await request(message);
+        // Fire-and-forget - don't wait for response
+        send(message);
         this.scheduleStopDmTyping(recipientId);
-        } catch (error) {
-            console.error("Failed to send DM typing indicator:", error);
-        }
     }
 
     /**
@@ -110,7 +101,6 @@ export class TypingManager {
     async sendStopDmTyping(recipientId: number): Promise<void> {
         if (!this.authToken) return;
 
-        try {
         const message: StopDmTypingRequest = {
             type: "stopDmTyping",
             credentials: {
@@ -122,11 +112,9 @@ export class TypingManager {
             }
         };
 
-            await request(message);
+        // Fire-and-forget - don't wait for response
+        send(message);
         this.clearStopTypingTimeout(`dm_${recipientId}`);
-        } catch (error) {
-            console.error("Failed to send stop DM typing indicator:", error);
-        }
     }
 
     /**

frontend/src/core/updateManager.ts

@@ -6,7 +6,6 @@
  */
 
 import { openDB, type IDBPDatabase } from "idb";
-import type { WebSocketCredentials, WebSocketMessage } from "./types";
 
 interface UpdateMessage<T = any> {
     type: string;
@@ -72,28 +71,18 @@ export async function setLastSequence(seq: number): Promise<void> {
  * Process a batched updates message
  * @param message - The batched updates message from the server
  * @param handler - Function to handle individual updates
- * @param requestMissedFn - Optional function to request missed updates (for gap detection)
  */
 export async function processBatchedUpdates(
     message: BatchedUpdatesMessage,
-    handler: (update: UpdateMessage) => void,
+    handler: (update: UpdateMessage) => void
-    requestMissedFn?: (lastSeq: number) => Promise<void>
 ): Promise<void> {
     const { seq, updates } = message;
     const lastSeq = await getLastSequence();
     
-    // Check for gap
+    // Log gap for debugging, but don't try to recover (getUpdates doesn't work properly)
     if (seq !== lastSeq + 1 && lastSeq > 0) {
-        console.warn(`Update gap detected: expected ${lastSeq + 1}, got ${seq}`);
+        const gapSize = seq - (lastSeq + 1);
-        
+        console.warn(`Update gap detected: expected ${lastSeq + 1}, got ${seq} (gap size: ${gapSize}). Skipping ${gapSize} updates.`);
-        // Request missing updates if function provided
-        if (requestMissedFn) {
-            try {
-                await requestMissedFn(lastSeq);
-            } catch (error) {
-                console.error("Failed to request missed updates for gap:", error);
-            }
-        }
     }
     
     // Process all updates in the batch
@@ -104,23 +93,3 @@ export async function processBatchedUpdates(
     // Update last sequence number
     await setLastSequence(seq);
 }
-
-/**
- * Request missed updates from the server
- * @param lastSeq - The last sequence number we received
- * @param requestFn - Function to send the request to the server
- * @param credentials - Optional WebSocket credentials for authentication
- */
-export async function requestMissedUpdates(
-    lastSeq: number,
-    requestFn: (request: WebSocketMessage<{ lastSeq: number }>) => Promise<void>,
-    credentials?: WebSocketCredentials
-): Promise<void> {
-    if (lastSeq > 0) {
-        await requestFn({
-            type: "getUpdates",
-            data: { lastSeq },
-            credentials
-        });
-    }
-}

frontend/src/core/websocket.ts

@@ -12,7 +12,7 @@ import { CallSignalingHandler } from "./calls/signaling";
 import { onlineStatusManager } from "./onlineStatusManager";
 import { typingManager } from "./typingManager";
 import { useUserStore } from "@/state/user";
-import { getLastSequence, processBatchedUpdates, requestMissedUpdates } from "./updateManager";
+import { processBatchedUpdates } from "./updateManager";
 import { getAuthToken } from "@/core/api/user/auth";
 
 interface HttpError extends Error {
@@ -161,21 +161,10 @@ function setupEventHandlers(): void {
 
             // Handle batched updates
             if (response.type === "updates" && "seq" in response && "updates" in response) {
-                // Create function to request missed updates with credentials
-                const token = getAuthToken();
-                const requestMissedFn = token ? async (lastSeq: number) => {
-                    await requestMissedUpdates(lastSeq, async (req) => {
-                        await request(req);
-                    }, {
-                        scheme: "Bearer",
-                        credentials: token
-                    });
-                } : undefined;
-                
                 await processBatchedUpdates(response as any, (update) => {
                     // Route individual updates to appropriate handlers
                     handleUpdate(update);
-                }, requestMissedFn);
+                });
                 return;
             }
 
@@ -250,20 +239,9 @@ function setupEventHandlers(): void {
                     console.error("Failed to send ping on reconnect:", error);
                 }
                 
-                // Send last sequence number and request missed updates on reconnect
+                // Note: We don't request missed updates on reconnect because getUpdates
-                // Wait a bit for ping to complete authentication
+                // doesn't properly return updates (they're sent directly via WebSocket
-                await delay(100);
+                // but the client can't handle them). Gaps will be logged but not recovered.
-                
-                try {
-                    const lastSeq = await getLastSequence();
-                    if (lastSeq > 0) {
-                        await requestMissedUpdates(lastSeq, async (req) => {
-                            await request(req);
-                        }, credentials);
-                    }
-                } catch (error) {
-                    console.error("Failed to request missed updates:", error);
-                }
             }
         } catch (error) {
             console.error("Failed to authenticate on reconnect:", error);
@@ -359,6 +337,22 @@ export function request<Request, Response = any>(payload: WebSocketMessage<Reque
     });
 }
 
+/**
+ * Send a WebSocket message without waiting for a response (fire-and-forget)
+ * Useful for typing indicators and other non-critical messages
+ */
+export function send<T = unknown>(payload: WebSocketMessage<T>): void {
+    if (websocket.readyState !== WebSocket.OPEN) {
+        console.warn("WebSocket is not open, cannot send message");
+        return;
+    }
+    try {
+        websocket.send(JSON.stringify(payload));
+    } catch (error) {
+        console.error("Failed to send WebSocket message:", error);
+    }
+}
+
 // --------------
 // Initialization
 // --------------

frontend/src/pages/auth/AuthPage.tsx

@@ -1,12 +1,13 @@
 import { AuthContainer } from "./Auth";
 import { useState, useEffect, useRef, useLayoutEffect, useCallback, type RefObject } from "react";
-import { useNavigate, useSearchParams } from "react-router-dom";
+import { useNavigate, useSearchParams, Navigate } from "react-router-dom";
 import { motion, AnimatePresence } from "motion/react";
 import useDownloadAppScreen from "@/core/hooks/useDownloadAppScreen";
 import { LoginForm } from "./LoginForm";
 import { RegisterForm } from "./RegisterForm";
 import type { Variants, Transition } from "motion/react";
 import styles from "./auth.module.scss";
+import { useUserStore } from "@/state/user";
 
 const slideVariants: Variants = {
     enter: (direction: number) => ({
@@ -37,8 +38,8 @@ const slideTransition: Transition = {
 export default function AuthPage() {
     const [searchParams] = useSearchParams();
     const { navigate: navigateDownloadApp } = useDownloadAppScreen();
-    if (navigateDownloadApp) return navigateDownloadApp;
     const navigate = useNavigate();
+    const { user } = useUserStore();
     
     const [direction, setDirection] = useState(0);
     const prevMode = useRef(searchParams.get("mode") || "login");
@@ -91,6 +92,12 @@ export default function AuthPage() {
         };
     }, [currentMode]);
 
+    // Now we can do conditional returns after all hooks are called
+    if (navigateDownloadApp) return navigateDownloadApp;
+    if (user.authToken && user.currentUser) {
+        return <Navigate to="/chat" replace />;
+    }
+    
     function switchMode(newMode: "login" | "register") {
         navigate(`/auth?mode=${newMode}`, { replace: true });
     }

frontend/src/pages/auth/LoginForm.tsx

@@ -93,14 +93,30 @@ export function LoginForm({ onSwitchMode }: LoginFormProps) {
                 try {
                     await api.user.auth.ensureKeysOnLogin(password, data.token);
                     
-                    // Initialize Signal Protocol after keys are set up
+                    // Initialize Signal Protocol after keys are set up (non-blocking)
                     if (data.user?.id) {
+                        // Run Signal Protocol initialization in background to avoid blocking navigation
+                        (async () => {
+                            try {
                                 const { SignalProtocolService } = await import("@/utils/crypto/signalProtocol");
-                        const { uploadPreKeyBundle } = await import("@/core/api/crypto");
+                                const { uploadPreKeyBundle, uploadAllPreKeys } = await import("@/core/api/crypto/prekeys");
-                        const signalService = new SignalProtocolService(data.user.id.toString());
+                                const signalService = new SignalProtocolService(data.user!.id.toString());
                                 await signalService.initialize();
+                                
+                                // Upload base bundle with one prekey (for backward compatibility)
                                 const bundle = await signalService.getPreKeyBundle();
                                 await uploadPreKeyBundle(bundle, data.token);
+                                
+                                // Upload all prekeys for server-side rotation
+                                const baseBundle = await signalService.getBaseBundle();
+                                const prekeys = await signalService.getAllPreKeys();
+                                await uploadAllPreKeys(baseBundle, prekeys, data.token);
+                                
+                                console.log(`Uploaded ${prekeys.length} prekeys to server`);
+                            } catch (e) {
+                                console.error("Key setup failed:", e);
+                            }
+                        })();
                     }
                 } catch (e) {
                     console.error("Key setup failed:", e);

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

@@ -124,7 +124,9 @@ export function useDM() {
                                 lastMessageContent = formatDMMessageContent(decryptedData.data.content, conv.lastMessage.senderId, user.currentUser?.id!);
                             }
                         } catch (error) {
-                            console.error("Failed to decrypt last message for user", conv.user.id, error);
+                            // Silently fail for last message decryption - it's not critical
+                            // The message will just show "No messages" instead
+                            console.debug("Failed to decrypt last message for user", conv.user.id, error);
                         }
                     }
 

frontend/src/pages/chat/ui/right/Message.tsx

@@ -6,11 +6,12 @@ import { parse } from "marked";
 import { escape as escapeHtml } from "he";
 import { useEffect, useState, useRef, useMemo } from "react";
 import api from "@/core/api";
-import { ecdhSharedSecret, deriveWrappingKey } from "@/utils/crypto/asymmetric";
 import { importAesGcmKey, aesGcmDecrypt } from "@/utils/crypto/symmetric";
 import { useUserStore } from "@/state/user";
 import { useProfileStore } from "@/state/profile";
 import { StatusBadge } from "@/core/components/StatusBadge";
+import { SignalProtocolService } from "@/utils/crypto/signalProtocol";
+import { removePadding } from "@/utils/crypto/obfuscation";
 import { ub64 } from "@/utils/utils";
 import { useImmer } from "use-immer";
 import { createPortal } from "react-dom";
@@ -212,7 +213,7 @@ export function Message({ message, isAuthor, onContextMenu, onReactionClick, isD
     }, [message.files, isDm, decryptedFiles]);
 
     async function decryptFile(file: Attachment): Promise<string | null> {
-        if (!file.encrypted || !isDm || !user.authToken || !dmRecipientPublicKey || !dmEnvelope) return null;
+        if (!file.encrypted || !isDm || !user.authToken || !dmEnvelope || !user.currentUser?.id) return null;
 
         // Check if already decrypted
         if (decryptedFiles.has(file.path)) {
@@ -220,7 +221,6 @@ export function Message({ message, isAuthor, onContextMenu, onReactionClick, isD
         }
 
         try {
-            // no-op decrypt indicator removed from UI
             // Fetch encrypted file
             const response = await fetch(file.path, {
                 headers: api.user.auth.getAuthHeaders(user.authToken!)
@@ -229,19 +229,36 @@ export function Message({ message, isAuthor, onContextMenu, onReactionClick, isD
 
             const encryptedData = await response.arrayBuffer();
 
-            // Get current user's keys
+            // Decrypt the master key using Signal Protocol
-            const keys = api.user.auth.getCurrentKeys();
+            const signalService = new SignalProtocolService(user.currentUser.id.toString());
-            if (!keys) throw new Error("Keys not initialized");
+            const senderId = dmEnvelope.senderId;
             
-            // Derive shared secret with the recipient's public key
+            // Remove padding from wrappedMk (backward compatible)
-            const shared = await ecdhSharedSecret(keys.privateKey, ub64(dmRecipientPublicKey));
+            let wrappedMkStr: string;
+            try {
+                wrappedMkStr = removePadding(dmEnvelope.wrappedMk);
+            } catch {
+                // If padding removal fails, assume it's an old message without padding
+                wrappedMkStr = dmEnvelope.wrappedMk;
+            }
             
-            // Derive wrapping key using the salt from the DM envelope
+            // Parse wrappedMk - it's a JSON string containing Signal Protocol encrypted data
-            const wkRaw = await deriveWrappingKey(shared, ub64(dmEnvelope.salt), new Uint8Array([1]));
+            let mk: Uint8Array;
-            const wk = await importAesGcmKey(wkRaw);
+            try {
-
+                const encryptedMk = JSON.parse(wrappedMkStr);
-            // Unwrap the message key
+                if (encryptedMk.type && encryptedMk.body) {
-            const mk = await aesGcmDecrypt(wk, ub64(dmEnvelope.iv2), ub64(dmEnvelope.wrappedMk));
+                    // Signal Protocol encrypted
+                    const mkBase64 = await signalService.decryptMessage(senderId, encryptedMk);
+                    mk = new Uint8Array(
+                        atob(mkBase64).split("").map(c => c.charCodeAt(0))
+                    );
+                } else {
+                    throw new Error("Invalid Signal Protocol message format");
+                }
+            } catch (error) {
+                console.error("Failed to decrypt master key with Signal Protocol:", error);
+                throw error;
+            }
 
             // Decrypt the file using the message key
             const iv = new Uint8Array(encryptedData, 0, 12);

frontend/src/pages/chat/ui/right/panels/DMPanel.ts

@@ -53,6 +53,8 @@ export class DMPanel extends MessagePanel {
     clearMessages(): void {
         super.clearMessages();
         this.messagesLoaded = false;
+        this.processedMessageIds.clear();
+        this.failedDecryptionIds.clear();
     }
 
     private async parseTextPayload(env: DmEnvelope, decryptedMessages: Message[]) {
@@ -111,6 +113,10 @@ export class DMPanel extends MessagePanel {
 
             for (const env of messages) {
                 try {
+                    // Mark as processed to prevent duplicates
+                    if (env.id) {
+                        this.processedMessageIds.add(env.id);
+                    }
                     const dmMsg = await this.parseTextPayload(env, decryptedMessages);
                     decryptedMessages.push(dmMsg);
 
@@ -118,7 +124,15 @@ export class DMPanel extends MessagePanel {
                         maxIncomingId = env.id;
                     }
                 } catch (error) {
-                    console.error("Error decrypting message:", error);
+                    // Log warning with deduplication to avoid console spam
+                    if (env.id && !this.failedDecryptionIds.has(env.id)) {
+                        this.failedDecryptionIds.add(env.id);
+                        console.warn(`Failed to decrypt DM ${env.id}:`, error instanceof Error ? error.message : String(error));
+                    }
+                    // Remove from processed set if decryption failed
+                    if (env.id) {
+                        this.processedMessageIds.delete(env.id);
+                    }
                 }
             }
 
@@ -165,7 +179,7 @@ export class DMPanel extends MessagePanel {
                         const dmMsg = await this.parseTextPayload(env, decryptedMessages);
                         decryptedMessages.push(dmMsg);
                     } catch (error) {
-                        console.error("Error decrypting message:", error);
+                        // Silently skip messages that can't be decrypted
                     }
                 }
                 
@@ -204,7 +218,6 @@ export class DMPanel extends MessagePanel {
             } else {
                 await sendDmWithFiles(
                     this.dmData.userId,
-                    this.dmData.publicKey,
                     json,
                     files,
                     this.currentUser.authToken
@@ -212,6 +225,16 @@ export class DMPanel extends MessagePanel {
             }
         } catch (error) {
             console.error("Failed to send DM:", error);
+            
+            // Check if it's a prekey exhaustion error
+            const { PrekeyExhaustedError } = await import("@/core/api/crypto/prekeys");
+            if (error instanceof PrekeyExhaustedError) {
+                const { alert } = await import("@/core/components/AlertDialog");
+                await alert({
+                    headline: "Cannot Send Message",
+                    description: "The recipient's encryption keys are temporarily unavailable. They need to come online to refresh their keys. This ensures maximum privacy and security."
+                });
+            }
         }
     }
 
@@ -228,14 +251,33 @@ export class DMPanel extends MessagePanel {
     }
 
 
+    // Track processed message IDs to prevent duplicates
+    private processedMessageIds: Set<number> = new Set();
+    private failedDecryptionIds: Set<number> = new Set(); // Track messages that failed decryption to avoid spam
+
     // Handle incoming WebSocket DM messages
     async handleWebSocketMessage(response: DMWebSocketMessage): Promise<void> {
+        // Only process actual DM messages, not typing indicators or other events
         if (response.type === "dmNew" && this.dmData) {
             const envelope = response.data;
 
+            // Validate envelope has required fields
+            if (!envelope || !envelope.ciphertext || !envelope.senderId || !envelope.id) {
+                console.warn("Invalid DM envelope received, skipping");
+                return;
+            }
+
+            // Skip if we've already processed this message
+            if (this.processedMessageIds.has(envelope.id)) {
+                return;
+            }
+
             // If this is for the active DM conversation
             if (envelope.senderId === this.dmData.userId || envelope.recipientId === this.dmData.userId) {
                 try {
+                    // Mark as processed before attempting decryption
+                    this.processedMessageIds.add(envelope.id);
+                    
                     const dmMsg = await this.parseTextPayload(envelope, this.getMessages());
 
                     // Check if this is a confirmation of a message we sent
@@ -258,7 +300,15 @@ export class DMPanel extends MessagePanel {
                         this.setLastReadId(this.dmData.userId, Math.max(this.getLastReadId(this.dmData.userId), envelope.id));
                     }
                 } catch (error) {
-                    console.error("Failed to decrypt incoming DM:", error);
+                    // Only log each failed message once to avoid console spam
+                    if (envelope.id && !this.failedDecryptionIds.has(envelope.id)) {
+                        this.failedDecryptionIds.add(envelope.id);
+                        console.warn(`Failed to decrypt DM ${envelope.id}:`, error instanceof Error ? error.message : String(error));
+                    }
+                    // Remove from processed set so we can retry if needed
+                    if (envelope.id) {
+                        this.processedMessageIds.delete(envelope.id);
+                    }
                 }
             }
         }
@@ -315,6 +365,7 @@ export class DMPanel extends MessagePanel {
         this.dmData = null;
         this.messagesLoaded = false;
         this.clearMessages();
+        this.failedDecryptionIds.clear(); // Clear failed decryption tracking
         this.updateState({
             id: "dm",
             title: "Select a user",
@@ -383,7 +434,7 @@ export class DMPanel extends MessagePanel {
                 reply_to_id: msg?.reply_to?.id ?? undefined
             }
         };
-        api.chats.dm.edit(messageId, this.dmData.publicKey, JSON.stringify(payload), this.currentUser.authToken).catch((e) => {
+        api.chats.dm.edit(messageId, this.dmData.userId, JSON.stringify(payload), this.currentUser.authToken).catch((e) => {
             console.error("Failed to edit DM:", e);
         });
     }

frontend/src/utils/crypto/obfuscation.ts

@@ -0,0 +1,76 @@
+import { randomBytes } from "./kdf";
+
+/**
+ * Padding sizes that look like normal HTTP/WebSocket traffic
+ * These sizes are common in real web traffic to avoid fingerprinting
+ */
+const PADDING_BUCKETS = [64, 128, 256, 512, 1024, 2048, 4096];
+
+/**
+ * Adds padding to a message to make it resistant to size-based fingerprinting
+ * Pads to the nearest bucket size to make all messages look similar
+ * @param data - The data to pad
+ * @returns Padded data with padding length prefix
+ */
+export function addPadding(data: string): string {
+    const dataBytes = new TextEncoder().encode(data);
+    const dataSize = dataBytes.length;
+    
+    // Find the smallest bucket that fits the data
+    let targetSize = PADDING_BUCKETS[PADDING_BUCKETS.length - 1];
+    for (const bucket of PADDING_BUCKETS) {
+        if (bucket >= dataSize + 4) { // +4 for padding length header
+            targetSize = bucket;
+            break;
+        }
+    }
+    
+    // Calculate padding needed (subtract data size and 4-byte length header)
+    const paddingSize = targetSize - dataSize - 4;
+    const padding = randomBytes(Math.max(0, paddingSize));
+    
+    // Create padded message: [4-byte length][data][random padding]
+    const lengthBytes = new Uint8Array(4);
+    const view = new DataView(lengthBytes.buffer);
+    view.setUint32(0, dataSize, true); // Little-endian
+    
+    const padded = new Uint8Array(4 + dataSize + padding.length);
+    padded.set(lengthBytes, 0);
+    padded.set(dataBytes, 4);
+    padded.set(padding, 4 + dataSize);
+    
+    // Return as base64 for easy transmission
+    // Use chunked approach to avoid "Maximum call stack size exceeded" for large arrays
+    // Convert Uint8Array to base64 in chunks
+    const chunkSize = 8192;
+    let binary = '';
+    for (let i = 0; i < padded.length; i += chunkSize) {
+        const chunk = padded.slice(i, i + chunkSize);
+        binary += String.fromCharCode.apply(null, Array.from(chunk));
+    }
+    return btoa(binary);
+}
+
+/**
+ * Removes padding from a message
+ * @param paddedData - The padded data (base64)
+ * @returns Original unpadded data
+ */
+export function removePadding(paddedData: string): string {
+    try {
+        const padded = Uint8Array.from(atob(paddedData), c => c.charCodeAt(0));
+        
+        // Read length from first 4 bytes
+        const view = new DataView(padded.buffer);
+        const dataSize = view.getUint32(0, true); // Little-endian
+        
+        // Extract original data
+        const data = padded.slice(4, 4 + dataSize);
+        return new TextDecoder().decode(data);
+    } catch (error) {
+        // If padding removal fails, assume it's an old message without padding
+        return paddedData;
+    }
+}
+
+

frontend/src/utils/crypto/signalProtocol.ts

@@ -8,10 +8,12 @@ import {
     SessionCipher,
     KeyHelper,
     SignalProtocolAddress,
-    type DeviceType
+    type DeviceType,
+    type KeyPairType
 } from "@privacyresearch/libsignal-protocol-typescript";
 import { SignalProtocolStorage } from "./signalStorage";
 import { b64, ub64 } from "../utils";
+import api from "@/core/api";
 
 // Helper to ensure we get a proper ArrayBuffer (not SharedArrayBuffer)
 function toArrayBuffer(buffer: ArrayBuffer | SharedArrayBuffer): ArrayBuffer {
@@ -40,6 +42,13 @@ export interface PreKeyBundleData {
 export class SignalProtocolService {
     private storage: SignalProtocolStorage;
     
+    // Prekey configuration constants
+    private static readonly PREKEY_COUNT = 20;
+    private static readonly PREKEY_REGEN_THRESHOLD = 5; // Regenerate when fewer than this many prekeys are left
+    private static readonly PREKEY_REGEN_COUNT = 10; // Number of prekeys to regenerate
+    private static readonly SIGNED_PREKEY_ID = 1;
+    private static readonly BATCH_SIZE = 10;
+
     constructor(userId: string) {
         this.storage = new SignalProtocolStorage(userId);
     }
@@ -64,20 +73,110 @@ export class SignalProtocolService {
         await this.storage.saveLocalRegistrationId(registrationId);
 
         // Generate signed prekey
-        const signedPreKeyId = 1;
+        const signedPreKey = await KeyHelper.generateSignedPreKey(identityKeyPair, SignalProtocolService.SIGNED_PREKEY_ID);
-        const signedPreKey = await KeyHelper.generateSignedPreKey(identityKeyPair, signedPreKeyId);
+        // Store both the key pair and its signature
-        await this.storage.storeSignedPreKey(signedPreKeyId, signedPreKey.keyPair);
+        await this.storage.storeSignedPreKey(
+            SignalProtocolService.SIGNED_PREKEY_ID, 
+            signedPreKey.keyPair, 
+            new Uint8Array(signedPreKey.signature)
+        );
 
-        // Store signature separately (we'll need it for the bundle)
+        // Generate prekeys (one-time keys for establishing new sessions)
-        // For now, we'll regenerate it when needed since storage doesn't store signatures
+        // Each new conversation consumes one prekey when the first message is sent
-
+        // Generation is non-blocking (yields to event loop), so this doesn't freeze the UI
-        // Generate prekeys (typically 100 prekeys)
+        for (let i = 1; i <= SignalProtocolService.PREKEY_COUNT; i++) {
-        const preKeyCount = 100;
-        for (let i = 1; i <= preKeyCount; i++) {
             const preKey = await KeyHelper.generatePreKey(i);
             await this.storage.storePreKey(i, preKey.keyPair);
+            
+            // Yield to event loop every batchSize keys to prevent UI freezing
+            if (i % SignalProtocolService.BATCH_SIZE === 0) {
+                await new Promise(resolve => setTimeout(resolve, 0));
             }
         }
+    }
+
+    /**
+     * Ensure signed prekey exists and is valid, regenerating if necessary
+     */
+    private async ensureSignedPreKey(identityKeyPair: KeyPairType): Promise<{ keyPair: KeyPairType; signature: Uint8Array }> {
+        let signature = await this.storage.loadSignedPreKeySignature(SignalProtocolService.SIGNED_PREKEY_ID);
+        let signedPreKey = await this.storage.loadSignedPreKey(SignalProtocolService.SIGNED_PREKEY_ID);
+        
+        if (!signedPreKey || !signature) {
+            // Signed prekey or signature missing - regenerate both to ensure consistency
+            const signedPreKeyWithSig = await KeyHelper.generateSignedPreKey(identityKeyPair, SignalProtocolService.SIGNED_PREKEY_ID);
+            await this.storage.storeSignedPreKey(
+                SignalProtocolService.SIGNED_PREKEY_ID, 
+                signedPreKeyWithSig.keyPair, 
+                new Uint8Array(signedPreKeyWithSig.signature)
+            );
+            signedPreKey = signedPreKeyWithSig.keyPair;
+            signature = new Uint8Array(signedPreKeyWithSig.signature);
+        }
+        
+        return { keyPair: signedPreKey, signature };
+    }
+    
+    /**
+     * Find an available prekey, regenerating if necessary
+     */
+    private async findOrRegeneratePreKey(): Promise<{ keyPair: KeyPairType; keyId: number }> {
+        // Find the first available prekey
+        let preKey: KeyPairType | undefined;
+        let preKeyId = 0;
+        let availableCount = 0;
+        
+        for (let i = 1; i <= SignalProtocolService.PREKEY_COUNT; i++) {
+            const candidate = await this.storage.loadPreKey(i);
+            if (candidate) {
+                availableCount++;
+                if (!preKey) {
+                    preKey = candidate;
+                    preKeyId = i;
+                }
+            }
+        }
+        
+        // If we're running low on prekeys, regenerate more proactively
+        if (availableCount < SignalProtocolService.PREKEY_REGEN_THRESHOLD) {
+            console.warn(`Low on prekeys (${availableCount} remaining), regenerating...`);
+            
+            // Find the next available ID to regenerate from
+            let nextId = SignalProtocolService.PREKEY_COUNT + 1;
+            for (let i = 1; i <= SignalProtocolService.PREKEY_COUNT; i++) {
+                const existing = await this.storage.loadPreKey(i);
+                if (!existing) {
+                    nextId = i;
+                    break;
+                }
+            }
+            
+            // Regenerate prekeys starting from nextId
+            for (let i = 0; i < SignalProtocolService.PREKEY_REGEN_COUNT; i++) {
+                const keyId = nextId + i;
+                const existing = await this.storage.loadPreKey(keyId);
+                if (!existing) {
+                    const newPreKey = await KeyHelper.generatePreKey(keyId);
+                    await this.storage.storePreKey(keyId, newPreKey.keyPair);
+                    if (!preKey) {
+                        preKey = newPreKey.keyPair;
+                        preKeyId = keyId;
+                    }
+                }
+            }
+        }
+        
+        // Emergency fallback if still no prekey
+        if (!preKey) {
+            console.error("No prekeys available, emergency regeneration...");
+            const newPreKey = await KeyHelper.generatePreKey(1);
+            await this.storage.storePreKey(1, newPreKey.keyPair);
+            preKey = newPreKey.keyPair;
+            preKeyId = 1;
+        }
+        
+        return { keyPair: preKey, keyId: preKeyId };
+    }
     
     /**
      * Get prekey bundle for this user to share with others
@@ -93,37 +192,74 @@ export class SignalProtocolService {
             throw new Error("Registration ID not found");
         }
 
-        const signedPreKey = await this.storage.loadSignedPreKey(1);
+        const { keyPair: signedPreKey, signature } = await this.ensureSignedPreKey(identityKeyPair);
-        if (!signedPreKey) {
+        const { keyPair: preKey, keyId: preKeyId } = await this.findOrRegeneratePreKey();
-            throw new Error("Signed prekey not found");
-        }
-
-        // Regenerate signed prekey to get signature (since storage doesn't store it)
-        // In production, you'd store the signature separately
-        const signedPreKeyWithSig = await KeyHelper.generateSignedPreKey(identityKeyPair, 1);
-        await this.storage.storeSignedPreKey(1, signedPreKeyWithSig.keyPair);
-
-        // Get a prekey to include
-        const preKey = await this.storage.loadPreKey(1);
-        if (!preKey) {
-            throw new Error("No prekeys available");
-        }
 
         return {
             registrationId: registrationId,
             identityKey: b64(new Uint8Array(identityKeyPair.pubKey)),
             signedPreKey: {
-                keyId: 1,
+                keyId: SignalProtocolService.SIGNED_PREKEY_ID,
                 publicKey: b64(new Uint8Array(signedPreKey.pubKey)),
-                signature: b64(new Uint8Array(signedPreKeyWithSig.signature))
+                signature: b64(signature)
             },
             preKey: {
-                keyId: 1,
+                keyId: preKeyId,
                 publicKey: b64(new Uint8Array(preKey.pubKey))
             }
         };
     }
     
+    /**
+     * Get all available prekeys for uploading to the server
+     */
+    async getAllPreKeys(): Promise<Array<{ keyId: number; publicKey: string }>> {
+        const prekeys: Array<{ keyId: number; publicKey: string }> = [];
+        
+        // Check all possible prekey IDs (including regenerated ones beyond initial count)
+        // We check up to PREKEY_COUNT + PREKEY_REGEN_COUNT to include regenerated prekeys
+        const maxPreKeyId = SignalProtocolService.PREKEY_COUNT + SignalProtocolService.PREKEY_REGEN_COUNT;
+        
+        for (let i = 1; i <= maxPreKeyId; i++) {
+            const prekey = await this.storage.loadPreKey(i);
+            if (prekey) {
+                prekeys.push({
+                    keyId: i,
+                    publicKey: b64(new Uint8Array(prekey.pubKey))
+                });
+            }
+        }
+        
+        return prekeys;
+    }
+    
+    /**
+     * Get the base bundle (without prekey) for uploading all prekeys
+     */
+    async getBaseBundle(): Promise<Omit<PreKeyBundleData, "preKey">> {
+        const identityKeyPair = await this.storage.getIdentityKeyPair();
+        if (!identityKeyPair) {
+            throw new Error("Signal Protocol not initialized");
+        }
+
+        const registrationId = await this.storage.getLocalRegistrationId();
+        if (!registrationId) {
+            throw new Error("Registration ID not found");
+        }
+
+        const { keyPair: signedPreKey, signature } = await this.ensureSignedPreKey(identityKeyPair);
+
+        return {
+            registrationId: registrationId,
+            identityKey: b64(new Uint8Array(identityKeyPair.pubKey)),
+            signedPreKey: {
+                keyId: SignalProtocolService.SIGNED_PREKEY_ID,
+                publicKey: b64(new Uint8Array(signedPreKey.pubKey)),
+                signature: b64(signature)
+            }
+        };
+    }
+
     /**
      * Process a prekey bundle from another user and establish a session
      */
@@ -163,41 +299,187 @@ export class SignalProtocolService {
 
         const sessionCipher = new SessionCipher(this.storage, address);
         const plaintextBuffer = toArrayBuffer(new TextEncoder().encode(plaintext).buffer);
-        const { type, body } = await sessionCipher.encrypt(plaintextBuffer);
+        const encryptResult = await sessionCipher.encrypt(plaintextBuffer);
+        const { type, body } = encryptResult;
 
         if (!body) {
             throw new Error("Encryption failed: no body in ciphertext");
         }
 
-        // ciphertext.body is a base64 string, but we need to convert it properly
+        // The library returns body as ArrayBuffer or Uint8Array, we need to convert it to base64 string
-        // According to the library, body is a serialized protobuf message as base64 string
+        // Always convert to Uint8Array first, then to base64, regardless of input type
-        return { type, body };
+        let bodyArray: Uint8Array;
+        const bodyAny = body as any;
+        
+        if (typeof body === "string") {
+            // String input - check if it's already base64
+            const base64Regex = /^[A-Za-z0-9+/]*={0,2}$/;
+            if (base64Regex.test(body)) {
+                // Already base64, use as-is
+                bodyArray = ub64(body);
+            } else {
+                // String contains binary data, convert to Uint8Array
+                bodyArray = new Uint8Array([...body].map(c => c.charCodeAt(0)));
+            }
+        } else if (bodyAny instanceof Uint8Array) {
+            bodyArray = bodyAny;
+        } else if (bodyAny instanceof ArrayBuffer) {
+            bodyArray = new Uint8Array(bodyAny);
+        } else {
+            // Try to convert unknown type
+            if (bodyAny.buffer && bodyAny.buffer instanceof ArrayBuffer) {
+                bodyArray = new Uint8Array(bodyAny.buffer, bodyAny.byteOffset || 0, bodyAny.byteLength || bodyAny.buffer.byteLength);
+            } else {
+                bodyArray = new Uint8Array(bodyAny as ArrayBuffer);
+            }
+        }
+        
+        // Convert to base64
+        const bodyBase64 = b64(bodyArray);
+        
+        // Final validation - ensure the result is valid base64
+        const base64Regex = /^[A-Za-z0-9+/]*={0,2}$/;
+        if (!base64Regex.test(bodyBase64)) {
+            throw new Error(`Failed to convert body to base64: result contains invalid characters. Length: ${bodyBase64.length}`);
+        }
+        
+        // Test that it can be decoded
+        try {
+            atob(bodyBase64.substring(0, Math.min(4, bodyBase64.length)));
+        } catch (error) {
+            throw new Error(`Failed to convert body to base64: ${error instanceof Error ? error.message : String(error)}`);
+        }
+
+        return { type, body: bodyBase64 };
     }
 
     /**
      * Decrypt a message from a sender
      */
     async decryptMessage(senderId: number, ciphertext: { type: number; body: string }): Promise<string> {
+        if (!ciphertext.body || typeof ciphertext.body !== "string") {
+            throw new Error("Invalid ciphertext: body is missing or not a string");
+        }
+
         const address = new SignalProtocolAddress(senderId.toString(), 1);
 
         const sessionCipher = new SessionCipher(this.storage, address);
 
         // Handle both PreKeyWhisperMessage (type 3) and WhisperMessage (type 1)
+        // ciphertext.body is a base64 string from the Signal Protocol library
+        let bodyBuffer: ArrayBuffer;
+        try {
             const { buffer, byteOffset, byteLength } = ub64(ciphertext.body);
-        const bodyBuffer = toArrayBuffer(buffer.slice(byteOffset, byteOffset + byteLength));
+            bodyBuffer = toArrayBuffer(buffer.slice(byteOffset, byteOffset + byteLength));
-        let plaintextBytes: ArrayBuffer;
+        } catch (error) {
+            throw new Error(`Failed to decode ciphertext body: ${error instanceof Error ? error.message : String(error)}`);
+        }
         
+        let plaintextBytes: ArrayBuffer;
+        try {
             if (ciphertext.type === 3) {
-            // PreKeyWhisperMessage
+                // PreKeyWhisperMessage - this will consume a prekey
+                // Count available prekeys before decryption
+                const prekeysBefore = await this.countAvailablePrekeys();
+                
                 plaintextBytes = await sessionCipher.decryptPreKeyWhisperMessage(bodyBuffer);
+                
+                // Check if a prekey was consumed (removed by the library)
+                const prekeysAfter = await this.countAvailablePrekeys();
+                if (prekeysBefore > prekeysAfter) {
+                    // A prekey was consumed - refresh the bundle in the background
+                    // This ensures new users can still message you while you're offline
+                    this.refreshPreKeyBundle().catch(err => 
+                        console.warn("Failed to refresh prekey bundle after consumption:", err)
+                    );
+                }
             } else {
-            // WhisperMessage
+                // WhisperMessage - uses existing session, no prekey consumed
                 plaintextBytes = await sessionCipher.decryptWhisperMessage(bodyBuffer);
             }
+        } catch (error) {
+            // Log detailed error information for debugging
+            const errorMessage = error instanceof Error ? error.message : String(error);
+            
+            // Handle different types of decryption errors
+            if (errorMessage.includes("Bad MAC")) {
+                console.warn(`Bad MAC error detected for sender ${senderId} (type ${ciphertext.type}). Session may be out of sync.`);
+                
+                // For both types, remove the session so next message can re-establish it
+                try {
+                    await this.storage.removeSession(address.toString());
+                    console.warn(`Removed corrupted session for sender ${senderId}. Sender needs to send a new message to re-establish session.`);
+                } catch (resetError) {
+                    console.error("Failed to remove session:", resetError);
+                }
+            } else if (errorMessage.includes("Tried to decrypt on a sending chain") || errorMessage.includes("No record for device")) {
+                // These errors indicate the session state is corrupted or missing
+                // Remove the session so it can be re-established
+                console.warn(`Session state error for sender ${senderId}: ${errorMessage}. Removing session.`);
+                try {
+                    await this.storage.removeSession(address.toString());
+                    console.warn(`Removed corrupted session for sender ${senderId}. Sender needs to send a new message to re-establish session.`);
+                } catch (resetError) {
+                    console.error("Failed to remove session:", resetError);
+                }
+            }
+            
+            console.error("Signal Protocol decryption failed:", {
+                senderId,
+                type: ciphertext.type,
+                bodyLength: ciphertext.body.length,
+                bodyFirst50: ciphertext.body.substring(0, 50),
+                bodyLast50: ciphertext.body.substring(Math.max(0, ciphertext.body.length - 50)),
+                bodyIsBase64: /^[A-Za-z0-9+/]*={0,2}$/.test(ciphertext.body),
+                error: errorMessage
+            });
+            throw new Error(`Failed to decrypt message: ${errorMessage}`);
+        }
 
         return new TextDecoder().decode(plaintextBytes);
     }
     
+    /**
+     * Count available prekeys
+     */
+    private async countAvailablePrekeys(): Promise<number> {
+        let count = 0;
+        const maxPreKeyId = SignalProtocolService.PREKEY_COUNT + SignalProtocolService.PREKEY_REGEN_COUNT;
+        
+        for (let i = 1; i <= maxPreKeyId; i++) {
+            const prekey = await this.storage.loadPreKey(i);
+            if (prekey) {
+                count++;
+            }
+        }
+        return count;
+    }
+    
+    /**
+     * Refresh prekey bundle after a prekey was consumed
+     * This ensures new users can still message you while you're offline
+     * Uploads all available prekeys to the server for rotation
+     */
+    private async refreshPreKeyBundle(): Promise<void> {
+        try {
+            const token = api.user.auth.getAuthToken();
+            if (!token) {
+                console.warn("No auth token, cannot refresh prekey bundle");
+                return;
+            }
+            
+            const baseBundle = await this.getBaseBundle();
+            const prekeys = await this.getAllPreKeys();
+            
+            // Upload all prekeys in the background
+            api.crypto.prekeys.uploadAllPreKeys(baseBundle, prekeys, token).catch(err => 
+                console.warn("Failed to upload all prekeys:", err)
+            );
+        } catch (error) {
+            console.error("Failed to refresh prekey bundle:", error);
+        }
+    }
+
     /**
      * Check if a session exists for a recipient
      */

frontend/src/utils/crypto/signalStorage.ts

@@ -69,9 +69,44 @@ async function getStore(storeName: keyof SignalDB, mode: IDBTransactionMode = "r
 }
 
 // Helper to convert Uint8Array to ArrayBuffer
-function toArrayBuffer(u8: Uint8Array | ArrayBuffer): ArrayBuffer {
+function toArrayBuffer(u8: Uint8Array | ArrayBuffer | ArrayBufferLike): ArrayBuffer {
     if (u8 instanceof ArrayBuffer) return u8;
-    return u8.buffer.slice(u8.byteOffset, u8.byteOffset + u8.byteLength);
+    
+    // Check if SharedArrayBuffer is available (requires COOP/COEP headers)
+    const SharedArrayBufferConstructor = typeof SharedArrayBuffer !== "undefined" ? SharedArrayBuffer : null;
+    
+    if (SharedArrayBufferConstructor && u8 instanceof SharedArrayBufferConstructor) {
+        // Convert SharedArrayBuffer to ArrayBuffer by copying
+        const view = new Uint8Array(u8);
+        const copy = new Uint8Array(view.length);
+        copy.set(view);
+        // copy.buffer is always ArrayBuffer for a newly created Uint8Array
+        return copy.buffer as ArrayBuffer;
+    }
+    
+    // Uint8Array case - buffer might be SharedArrayBuffer, so copy it
+    if (u8 instanceof Uint8Array) {
+        const buffer = u8.buffer;
+        if (SharedArrayBufferConstructor && buffer instanceof SharedArrayBufferConstructor) {
+            const copy = new Uint8Array(u8.length);
+            copy.set(u8);
+            // copy.buffer is always ArrayBuffer for a newly created Uint8Array
+            return copy.buffer as ArrayBuffer;
+        }
+        const sliced = buffer.slice(u8.byteOffset, u8.byteOffset + u8.byteLength);
+        // Ensure we return ArrayBuffer, not SharedArrayBuffer
+        if (SharedArrayBufferConstructor && sliced instanceof SharedArrayBufferConstructor) {
+            const copy = new Uint8Array(sliced);
+            // copy.buffer is always ArrayBuffer for a newly created Uint8Array
+            return copy.buffer as unknown as ArrayBuffer;
+        }
+        // TypeScript doesn't know that slice() returns ArrayBuffer when buffer is ArrayBuffer
+        // But we've already checked it's not SharedArrayBuffer, so it must be ArrayBuffer
+        return sliced as unknown as ArrayBuffer;
+    }
+    
+    // Fallback: treat as ArrayBuffer
+    return u8 as unknown as ArrayBuffer;
 }
 
 // Helper to convert ArrayBuffer to Uint8Array
@@ -90,7 +125,7 @@ export class SignalProtocolStorage implements StorageType {
     // Identity Key Management
     async getIdentityKeyPair(): Promise<KeyPairType | undefined> {
         const store = await getStore("identityKeys");
-        const result = await new Promise<{ publicKey: ArrayBuffer; privateKey: ArrayBuffer } | undefined>((resolve, reject) => {
+        const result = await new Promise<KeyPairType | undefined>((resolve, reject) => {
             const request = store.get(this.userId);
             request.onsuccess = () => {
                 const data = request.result;
@@ -165,7 +200,7 @@ export class SignalProtocolStorage implements StorageType {
     async loadPreKey(encodedAddress: string | number): Promise<KeyPairType | undefined> {
         const preKeyId = typeof encodedAddress === "number" ? encodedAddress : parseInt(encodedAddress, 10);
         const store = await getStore("preKeys");
-        const result = await new Promise<{ publicKey: ArrayBuffer; privateKey: ArrayBuffer } | undefined>((resolve, reject) => {
+        const result = await new Promise<KeyPairType | undefined>((resolve, reject) => {
             const request = store.get([this.userId, preKeyId]);
             request.onsuccess = () => {
                 const data = request.result;
@@ -213,7 +248,7 @@ export class SignalProtocolStorage implements StorageType {
     async loadSignedPreKey(keyId: number | string): Promise<KeyPairType | undefined> {
         const signedPreKeyId = typeof keyId === "number" ? keyId : parseInt(keyId, 10);
         const store = await getStore("signedPreKeys");
-        const result = await new Promise<{ publicKey: ArrayBuffer; privateKey: ArrayBuffer; keyId: number } | undefined>((resolve, reject) => {
+        const result = await new Promise<KeyPairType | undefined>((resolve, reject) => {
             const request = store.get(this.userId);
             request.onsuccess = () => {
                 const data = request.result;
@@ -232,21 +267,50 @@ export class SignalProtocolStorage implements StorageType {
         return result;
     }
 
-    async storeSignedPreKey(keyId: number | string, keyPair: KeyPairType): Promise<void> {
+    async storeSignedPreKey(keyId: number | string, keyPair: KeyPairType, signature?: Uint8Array): Promise<void> {
         const signedPreKeyId = typeof keyId === "number" ? keyId : parseInt(keyId, 10);
         const store = await getStore("signedPreKeys", "readwrite");
         await new Promise<void>((resolve, reject) => {
-            const request = store.put({
+            interface SignedPreKeyData {
+                userId: string;
+                keyId: number;
+                publicKey: Uint8Array;
+                privateKey: Uint8Array;
+                signature?: Uint8Array;
+            }
+            const data: SignedPreKeyData = {
                 userId: this.userId,
                 keyId: signedPreKeyId,
                 publicKey: toUint8Array(keyPair.pubKey),
                 privateKey: toUint8Array(keyPair.privKey)
-            });
+            };
+            if (signature) {
+                data.signature = toUint8Array(signature);
+            }
+            const request = store.put(data);
             request.onsuccess = () => resolve();
             request.onerror = () => reject(request.error);
         });
     }
     
+    async loadSignedPreKeySignature(keyId: number | string): Promise<Uint8Array | undefined> {
+        const signedPreKeyId = typeof keyId === "number" ? keyId : parseInt(keyId, 10);
+        const store = await getStore("signedPreKeys");
+        const result = await new Promise<{ signature?: Uint8Array } | undefined>((resolve, reject) => {
+            const request = store.get(this.userId);
+            request.onsuccess = () => {
+                const data = request.result;
+                if (!data || data.keyId !== signedPreKeyId) {
+                    resolve(undefined);
+                    return;
+                }
+                resolve(data.signature ? { signature: toUint8Array(data.signature) } : undefined);
+            };
+            request.onerror = () => reject(request.error);
+        });
+        return result?.signature;
+    }
+
     async removeSignedPreKey(keyId: number | string): Promise<void> {
         const store = await getStore("signedPreKeys", "readwrite");
         await new Promise<void>((resolve, reject) => {
@@ -263,7 +327,7 @@ export class SignalProtocolStorage implements StorageType {
         const deviceId = parts.length > 1 ? parts[1] : encodedAddress;
         
         const store = await getStore("sessions");
-        const result = await new Promise<{ record: string } | undefined>((resolve, reject) => {
+        const result = await new Promise<string | undefined>((resolve, reject) => {
             const request = store.get([this.userId, deviceId]);
             request.onsuccess = () => {
                 const data = request.result;
@@ -291,5 +355,18 @@ export class SignalProtocolStorage implements StorageType {
             request.onerror = () => reject(request.error);
         });
     }
+
+    async removeSession(encodedAddress: string): Promise<void> {
+        // encodedAddress format: "userId.deviceId"
+        const parts = encodedAddress.split(".");
+        const deviceId = parts.length > 1 ? parts[1] : encodedAddress;
+        
+        const store = await getStore("sessions", "readwrite");
+        await new Promise<void>((resolve, reject) => {
+            const request = store.delete([this.userId, deviceId]);
+            request.onsuccess = () => resolve();
+            request.onerror = () => reject(request.error);
+        });
+    }
 }
 

frontend/src/utils/utils.ts

@@ -33,7 +33,17 @@ export function delay(ms: number): Promise<void> {
 }
 
 
-export function b64(a: Uint8Array): string { return btoa(String.fromCharCode(...a)); }
+export function b64(a: Uint8Array): string {
+    // Use chunked approach to avoid "Maximum call stack size exceeded" for large arrays
+    // Process in chunks and use apply to avoid spreading large arrays
+    const chunkSize = 8192;
+    let binary = '';
+    for (let i = 0; i < a.length; i += chunkSize) {
+        const chunk = a.slice(i, i + chunkSize);
+        binary += String.fromCharCode.apply(null, Array.from(chunk));
+    }
+    return btoa(binary);
+}
 export function ub64(s: string): Uint8Array {
 	const bin = atob(s);
 	const arr = new Uint8Array(bin.length);