tenzro-device-key

Hardware-backed device keys for Tenzro — macOS/iOS Secure Enclave P-256 signing + ECIES secret-wrapping, plus a biometric KeystoreUnlocker for passkey-gated wallet persistence.

A device key is a non-extractable P-256 keypair living in the platform's hardware-rooted secure element. On macOS/iOS that is the Secure Enclave (via security-framework + kSecAttrTokenIDSecureEnclave), gated by Touch ID / Face ID. The private key never enters process memory.

Two capabilities

1. Signing (DeviceKey::sign_prehash) — sign a 32-byte digest; the OS triggers the user-presence (Touch ID / Face ID) ceremony.
2. Secret wrapping (DeviceKey::wrap_secret / unwrap_secret) — ECIES- encrypt an arbitrary secret to the device public key (no biometrics), and decrypt it with the private key (biometrics). The decrypt output is stable across calls, which makes this the right primitive for deriving a persistent keystore password.

SecureEnclaveUnlocker

SecureEnclaveUnlocker implements tenzro-keystore-unlock's KeystoreUnlocker. On first run it creates an SE key, generates a random keystore password, wraps it to the key, and persists the ciphertext. On later runs it reopens the key and unwraps the ciphertext (Touch ID) to recover the same password — so an embedded tenzro-node's FROST wallet persists across restarts.

use std::sync::Arc;
use tenzro_device_key::SecureEnclaveUnlocker;

let unlocker = Arc::new(SecureEnclaveUnlocker::under_data_dir(&node_config.data_dir));
let handle = tenzro_node::spawn_in_background_with_unlocker(node_config, unlocker).await?;

Persistence

Cross-restart unlock works on a plain Developer-ID build with no extra entitlements: the Secure-Enclave key is persisted in the legacy file (login) keychain via Location::DefaultFileKeychain, which sets kSecAttrIsPermanent without requiring the keychain-access-groups entitlement or a provisioning profile (those are needed only by the data-protection keychain — see Apple TN3137). Touch ID / Face ID still gates every signing operation. A later run reopens the key by label and unwraps the on-disk ciphertext to recover the same password. If the key is gone (a different machine, or a reset login keychain), the unlocker reports the wallet as unavailable and the node recreates it.

Non-Apple platforms currently compile to a stub backend.

License

Apache-2.0