Quick-unlock PIN

The recovery phrase is 12 words for a reason — strong entropy, no shortcuts. But re-deriving the master key from it takes ~700ms (Argon2id with 64MB memory). Fine when setting up a new device; tedious every single time the browser idle-locks.

The PIN is the shortcut.

What it does

When you set a PIN, the device:

1. Wraps your already-unlocked master key with Argon2id keyed on the PIN.
2. Stores the wrapped blob in localStorage (key syncbins-pin-v1) on this browser only.
3. On next unlock, prompts for the PIN instead of the 12 words (~500ms Argon2id per attempt vs ~700ms for the full phrase).

The phrase still works

The PIN doesn’t replace your recovery phrase — it sits alongside it. You can always fall back to “Unlock with recovery phrase” on the lock screen, and you must do so on every new device.

Setting one up

Settings → Encryption → Set a PIN / Change PIN / Remove PIN. Requirements today:

• Minimum 6 digits (numeric only)
• Confirmation must match

There are no rules yet for sequential digits or PIN history — keep it non-obvious anyway.

After saving, the lock screen offers PIN entry by default. Use recovery phrase remains available under other unlock methods.

On the mobile app

The mobile app uses the same PIN model with two differences that make it stronger and more convenient:

• The PIN-wrapped master key is stored in the OS keychain / Keystore, not plain storage — so an offline attack must defeat both the secure enclave and Argon2id.
• You can enable Face ID / Touch ID / fingerprint as a convenience on top of the PIN (the PIN is always the fallback and owns the 5-attempt lockout).
• The app locks when it goes to the background and wipes the master key from memory; the PIN or a biometric scan is required to return.

See Mobile apps → Unlocking.

What it isn’t

A PIN is convenience, not a second factor

The PIN doesn’t add much cryptographic strength on its own — a 6-digit PIN is low entropy. On the web client the wrapped blob lives in localStorage, so the PIN mainly protects against shoulder-surfing and casual access, not a determined attacker with disk access. (Mobile stores the wrapped key in the OS keychain, which raises the bar — see above.)

If your threat model includes someone getting your device while it’s idle-locked, set a strong device-level passcode (iOS/Android lockscreen, FileVault, BitLocker) — that’s where the real protection lives.

Failure modes

• Wrong PIN: Up to 5 attempts (PIN_MAX_ATTEMPTS). Each failure increments a counter in the PIN blob.
• Lockout after 5 failures: PIN blob is wiped — unlock with the 12-word recovery phrase, then set a new PIN if you want.
• Forgotten PIN: Same as lockout — phrase always works.
• Change/remove PIN: Settings → Encryption while the vault is unlocked (master key in memory).

Per-device, not per-account

PINs are local to the device. Setting one on your laptop doesn’t set one on your phone. This is intentional — losing your phone shouldn’t compromise your laptop’s quick unlock.

If you want the same PIN on every device, set it on every device. We don’t sync PINs.

Going deeper

How encryption works Where the PIN sits in the bigger picture (key derivation, wrapping).

Recovery scenarios What to do if you forget the PIN, lose the device, or lose both.