Bitcoin researchers propose a quantum-safe signature path with a wallet-state tradeoff

The current SHRINCS specification is marked Draft and says its formal security proof is still to be completed. The current reference implementation also warns that it is a work in progress and is not production-ready. Those limits are part of the news: the ecosystem is testing a migration design, not deploying one.

The proposal targets the block-space problem

Post-quantum signatures are generally larger than the Schnorr signatures Bitcoin uses today. CoinDesk reported that Blockstream estimated a Bitcoin using NIST's SLH-DSA scheme could fall from about 6.5 transactions per second to roughly 0.36 when every transaction used the larger signatures. Its SHRINCS estimate rises to about three transactions per second, with signatures beginning around 324 bytes and reaching 580 bytes in the compact path.

Those are modelled capacity comparisons, not observed mainnet throughput. The specification's design uses SHA-256, already familiar in Bitcoin, and combines a compact stateful signing path with a larger stateless fallback. The tradeoff is that wallets must preserve signing state correctly and prevent a stateful key from signing twice with the same one-time key.

The hard part is migration

A Bitcoin deployment would require a soft fork and broad agreement on the output and verification rules. Wallets would also have to handle backups, device replacement and state loss without silently creating unsafe signatures. The implementation repository's warning is therefore operationally important: a cryptographic design can be promising while still being unsafe to use with real funds.

The proposal lands alongside Ethereum's longer post-quantum roadmap, but the two networks face different migration paths. For Bitcoin, the next evidence is a completed security proof, peer review, implementation work and a concrete soft-fork process—not a token-price reaction or a claim that quantum attacks are imminent.