The one-time key that seals a wallet backup.

Every wallet has one secret that can move its funds. We back that master key up as an encrypted envelope pinned to public storage. The question is how one envelope opens through several recovery paths while none of them stores the key.

The device puts a key in the middle. It generates a single random key, used once, and seals the master key with it under AES-256-GCM. That one-time key, the Wallet Backup Key, is the only thing that opens the envelope.

The device then wraps that small key three independent ways: the phone's Secure Enclave, your iCloud Keychain, and a recovery code run through Argon2id. Any one of them unwraps it, and the backend holds none.

Sealing the master once leaves every recovery path guarding the same short key, kept in three places the backend cannot reach.