OffCode tor chat

Tor-only hosting

ChatServer binds 127.0.0.1 only. Tor Expert Bundle publishes a v3 .onion and forwards VirtualPort 80 (and the app port) to localhost; no clearnet chat listener. Optional Docker compose: ChatServer + Tor (no host ports).

• HiddenServiceVersion 3, ClientOnly 1, SafeLogging 1
• SOCKS disabled on the HS process (SOCKSPort 0)
• Open in Tor Browser: http://ADDRESS.onion/
• Client clearnet banner if the page host is not .onion / localhost

Rooms, invites & TTL

Open, password-protected, and/or hidden rooms with invite links and required per-message lifetime.

• Hidden rooms: not listed; join via ?invite= (+ password if locked)
• Message expiry required: 30 min … 1 week (default 8 h). No forever option
• E2EE attachments (images + small files) on the same SendEncrypted path
• Profile: hide date/time stamps; pick message time zone (Tor often shows UTC)
• Unique senderId per room; server binds send identity to the session

Browser encryption (pbkdf2-v2)

WebCrypto PBKDF2-HMAC-SHA256 (600 000 iterations) → AES-256-GCM. Separate v2 KDF domains for join proof vs room key on locked rooms so the server cannot derive the message key from join material.

• AAD binds roomId|senderId|nonce|clientSentAtUnixMs
• Locked: password stays in the browser — server-blind E2EE
• Open: key from torchat-open-material-v2:{roomId} — public by design
• Server stores join-proof hash as 250000:salt:hash (250k PBKDF2)
• 1:1 ECDH hybrid + safety number (3×5 decimal) for peer verify / TOFU
• No Double Ratchet yet; prefer short message retention if passwords may leak

Ciphertext storage

SQLCipher database under LocalAppData (Windows) or Docker volume. DPAPI / env key. Parameterized queries. Plaintext is never written to disk.

• Rooms + ciphertext envelopes only (encryption_version: pbkdf2-v2 / ecdh-hybrid-v1)
• Max 500 messages per room (oldest trimmed)
• Expired rows: secure_delete + WAL checkpoint / VACUUM
• Replay fingerprints + restart-gap reject via server_meta

Full Vanguards - Guard-Discovery Protection

A standard Tor Hidden Service chooses its entry (guard) nodes randomly on every circuit build. Over time a network-level adversary can watch which relays the server connects to and gradually narrow down the real server IP. This is called a guard-discovery attack and is especially dangerous for long-lived hidden services.

Self-host your own chat server & Best privacy