SeedHammer

The SeedHammer is a metal engraving machine especially suitable for backing up bitcoin multisig wallets onto steel – while also supporting singlesig in credit card size, suitable for hot or lukewarm storage and as gift cards.

Self-contained Multisig Backup
For the first time a backup solution solves the pitfall of multisig. It is not enough to backup the shares; the descriptor also needs to be backed up.

This is usually solved by saving the descriptor (or xpubs of all the shares) offline on paper or online in the cloud etc. But both solutions are insecure and vulnerable.

With SeedHammer a part of the descriptor is engraved on the backside of each plate in a clever way so that the quorum always is enough to not only sign a transaction but also recover the full wallet! See how easy recovery is in Sparrow Wallet and Nunchuk.

QR codes for easy spending and recovery
All data on the plates are accompanied with the same data represented as QR codes. This makes it easy not only to recover a wallet with a few scans but also very fast to load a stateless signer as the SeedSigner, Blockstream Jade, Specter DIY and Krux. SparrowWallet can also be used as a emergency recovery tool.

Air-gapped and secure
The machines is 100% air-gapped and can only communicate with the controller (same hardware as a SeedSigner) via USB.

The engraving pattern is timing insensitive in order to eliminate exfiltration of the seed words and seedQR via listeners. The sound profile of all private data is the same – see this video.

Read more about the machine on seedhammer.com