Security
How Linen is built · Brilliance Digital
The strongest privacy control is architectural: data that never reaches a server cannot leak from one. Linen is designed so the sensitive things stay on your hardware.
On your device
- Encrypted local store. Your mailbox syncs into an encrypted database on the device; the encryption key lives in the platform keystore, never in a file.
- Keystore-held credentials. OAuth tokens, IMAP passwords, and personal AI keys go through Keychain, Credential Manager, Keystore, or Secret Service.
- Tracker-stripped reading. Every remote image is removed from incoming mail before layout, so tracking pixels never fire.
Between devices
Multi-device setup uses a zero-knowledge vault: your credentials are encrypted on-device with keys derived from a 12-word recovery phrase (BIP39 → HKDF → XChaCha20-Poly1305, bound to each entry). Our servers store ciphertext and a key-check value, nothing that can decrypt it. A lost phrase costs nothing but reconnecting your mailboxes.
On our servers
- TLS for every connection; strict security headers; rate limits and request-size limits on every surface.
- Service-to-service calls authenticated with short-lived Ed25519-signed tokens in both directions.
- An append-only credit ledger with idempotent reserve and settle, so billing arithmetic is auditable.
- Authentication events land in an audit log; dependencies are scanned and patched continuously.
AI requests
AI actions run only when you invoke them, carry only the text you selected, and route through zero-data-retention channels. Token counts are logged for billing; content is not.
Reporting a vulnerability
If you find a security issue, write to support@linen.email with enough detail to reproduce it. We acknowledge within two business days, keep you informed while we fix it, and credit you if you would like. Please give us reasonable time to ship a fix before public disclosure.