Trezor is considering a Bitcoin (BTC) signature setup that would make wallet software track one-time keys, placing a complex security task with wallet makers if the network adopts SHRINCS.
SHRINCS is a hash-based signature proposal by cryptographer Mikhail Kudinov and Blockstream Research Director Jonas Nick. It offers reusable stateless signatures and stateful signatures built from one-time keys arranged in a tree. Trezor is weighing a default that uses the reusable mode, while leaving the smaller stateful option for advanced settings.
For users who choose the stateful mode, Trezor CTO Tomáš Sušánka said the wallet maker should handle the usage records. If a one-time key is mistakenly used again, exposed information may help an attacker create a valid signature and spend funds. Stateless signatures avoid that particular failure, but their larger size may increase signing time and affect transaction fees or other efficiency measures.
Sušánka said stateful signatures are “10 times smaller.” He called SHRINCS conservative, noting that its cryptographic foundations overlap with those used by SHA-256. The compact signatures come with an operational requirement: software needs a reliable record of earlier key use. Sušánka separately questioned how two Trezor devices using the same recovery seed could keep key-use state in sync.
Bitcoin has not adopted post-quantum signatures, and current proposals remain in draft form. Bitcoin transactions would still need a change to the network’s signature rules to gain post-quantum protection. Trezor’s Safe 7 adds a different safeguard: post-quantum cryptography for authenticating the wallet device.
Sušánka said moving potentially millions of users would take time and that the transition may require compromises. He urged developers to make migration options available before a transition begins.
