onionwire/docs/THREAT_MODEL.md

# OnionWire threat model (v1)

OnionWire is a two-party chat over Tor onion services. There is no chat server.

## Tor relays are not a chat server

Each install hosts its own v3 onion and dials friends’ onions through in-process Arti. Relays move cells; they never see plaintext, never store messages, and never hold a roster. Compromising a relay is not compromising OnionWire’s message store. The store is the sqlite file on the endpoint.

## Location updates are not a missing-person finder

A signed `loc` frame (`onion`, `ts`, `sig`) rewrites a friend’s locator **only if** that friend is already in the roster, the signature verifies against the pinned pubkey, and `ts` is newer. There is no directory, DHT, or introduction server. If you rotated while they were offline, they cannot find you until they F3-paste your new invite. OnionWire will not hunt for a missing person.

## Rotating the onion does not revoke a friend

`F4` changes the locator only. The identity key is unchanged. Anyone who already has your pubkey can still prove they are talking to you, and a later invite paste with the same `k` updates their row. To become a new person, `/wipe-all` (new identity key). There is no in-band unfriend/revoke in v1.

## Message bodies are encrypted at rest; keys are not

Chat bodies in sqlite are ChaCha20-Poly1305 (`nonce || ciphertext` in the `messages.plaintext` column). A random 32-byte data key is wrapped with Argon2id (same params as identity backup) from a non-empty passphrase. Salt + wrapped key live in `store_meta`. Unlock is fail-closed: wrong or empty passphrase does not open chat.

Identity secret key, friend public keys, and locators remain plaintext in the same db. The message key is not wrapped with `identity_sk` (that key is already on disk). A seized laptop still yields who you talk to and your identity unless you add OS/FDE. sqlcipher is out of v1. `/wipe` overwrites message bodies and vacuums; `/wipe-all` deletes the data dir.

## Fail closed

Peer onion down → send fails. Fingerprint mismatch vs the pinned key → hard fail, no send. Arti HS experimental: if it cannot publish, OnionWire stops; it does not fall back to C-tor.

## Profile is friend-visible, not a directory

A signed `prf` frame is shown to people who already have a session with you. Apply only for existing friends. There is still no name lookup, DHT, or public profile server. Anyone who already has a Noise session can see the profile you send them; that is not confidentiality against that friend.

## Monero sidecar is not a wallet

OnionWire never holds spend keys. Optional `ONIONWIRE_WALLET_RPC` talks HTTP to a user-hosted `monero-wallet-rpc`. A Noise friend can sign any `rcp`; the signature proves who sent the claim, not that a payment happened. `verified=1` only after a conjunctive RPC match: one `get_transfers` row with the same non-empty `txid`, `amount`, and `address`. Incoming `rcp` stays `verified=0` if RPC is down, errors, or no exact row. Subaddress reuse is the user’s wallet policy.

## Backup file is the identity

`/backup` writes the identity and Noise static secrets. Treat the file like `onionwire.db`. Restore overwrites self keys and does **not** rewrite the friends table.

## Rate limit is availability, not anonymity

Incoming rendezvous accepts are token-bucket limited (30/60s, burst 10). Excess is dropped without handshake. That is a DoS/availability control. It does not hide that you run an onion, and it is not a traffic-analysis defense.

## Out of v1

Prosody, XMPP, s2s, MAM, carbons, outbox, multi-device, DHT / name server, sqlcipher.