Split a seed phrase

Cutting a seed phrase in half and hiding each half in a different place feels clever and is not: each half halves the work of guessing the rest. Shamir splitting is the version that actually works — fewer parts than the threshold reveal zero information, and that is provable, not marketing.

SLIP-39, the standard your wallet already speaks

ShamirVault splits using SLIP-0039, the scheme Trezor and other wallets implement. That matters for one specific reason: the parts are not a private format of ours. They are twenty or thirty-three words that any compatible implementation reads. If this app disappeared tomorrow, your backup would still be recoverable.

The implementation is validated against the 45 official test vectors published by SatoshiLabs and Trezor — the fifteen valid ones recover the exact secret and the thirty invalid ones are rejected. That is the difference between being SLIP-39 and merely resembling it.

Paste your 12 or 24 words

You do not need the entropy in hexadecimal. Paste the recovery phrase you already have and the app converts it, because that is what SLIP-39 actually splits. When you recover it, you get your phrase back — not a row of hexadecimal that no wallet asked you for.

Groups, for a shared treasury

SLIP-39 has two levels: you can require two of three groups, each with its own internal threshold. It is the natural shape for a multisig backup or a company treasury, where the people are not interchangeable.

The passphrase, and one thing you must know

SLIP-39 lets you add a passphrase. It has a property that is deliberate and uncomfortable: any passphrase returns a secret. There is no way to tell whether the one you typed is the right one. That allows a decoy passphrase opening a different wallet, and it means a typo does not give you an error — it gives you an empty wallet.

The app warns about this where it matters and makes you check the copy. If you use a passphrase, check.

Offline, and no ads

Everything runs on your device. Install it as an app and it works with no connection, which for a seed phrase is what we would recommend. There are no ads, no analytics and no account: the privacy policy lists exactly what leaves your device, and it is a short list.