Sigil

Sealed by proof

Unlocks when someone proves they know the answer — without revealing it to us. Pick a witness, attach a riddle, share the link. The witness never leaves the recipient's browser.

1. What to seal

2. The riddle

The riddle is plaintext metadata — it travels in the envelope so the recipient sees it before unlocking. Don't put the answer in here.

3. The witness

Knowing the witness reveals nothing to us — Argon2id derives the key in your browser. Pick something with real entropy (a passphrase, not a 4-digit PIN).

Argon2id (64 MiB) · XChaCha20-Poly1305 · key wrap stays in your browser.