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The architecture is the privacy policy.

Cloud messengers promise not to look. FLVSH removes the place where looking happens — no servers, no accounts, no copy of anything outside your phone.

Cloud messengers vs FLVSH
PropertyCloud messengersFLVSH
InfrastructureTheir servers, their uptime, their rulesNo servers: the phones in the room are the network
IdentityPhone number or email requiredX25519 keypair generated on device — no signup
Works offlineDead without internetBuilt for airplane mode: BLE only, end to end
MetadataWho, when, how often — logged server-sideNothing to log with: traffic never leaves the mesh
EncryptionE2E, but the operator routes every byteChaCha20-Poly1305; relays see only ciphertext
Message historyCloud backups you don't controlLocal SQLite only, with disappearing messages
RangeGlobal, while the grid is upThe room by radio, the crowd by mesh relay

The cryptography is deliberately boring: X25519 key agreement and ChaCha20-Poly1305 authenticated encryption from audited RustCrypto implementations, in one shared Rust core compiled into both apps. No novel primitives, no proprietary protocol — just a network made of the phones themselves.