Project
Coldstar: an air-gapped signer on any USB drive
Hardware-grade signing without a hardware wallet.
Coldstar boots a minimal Alpine Linux image from a USB stick, generates keys offline and signs transactions on a machine that never touches the network. The signer holds key material in memory only, and exposes it for about 100 microseconds before wiping it.
The flow is simple. You build the transaction on a connected machine, carry it to the air-gapped USB, sign it there, and broadcast the signed result.
The repo’s README reports 107 wallets created and 37 still signing. Those are the project’s own numbers, not independent figures.
Product page: coldstar.dev. Source: coldstar-colosseum. The work page has the longer case study.