The first fully specified post-quantum signature scheme for Bitcoin has been proposed to the Bitcoin mailing list.

The proposal introduces a full specification for “SHRINCS,” a hash-based signature scheme initially conceived by Jonas Nick and Mikhail Kudinov of Blockstream Research — with specification details added by new co-authors Conduition, Remix7531 and BIP 360 co-author Ethan Heilman.

Today, I’m honored to share a full whiteboard explanation of the scheme by its co-author Conduition, as well as thorough discussion of the scheme’s key tradeoffs when compared to Bitcoin’s existing elliptic-curve signatures and competing post-quantum alternatives.

In more detail, this interview includes:

— A full whiteboard walkthrough of the scheme’s key components and its relationship to the NIST-standardized scheme SPHINCS+

— SHRINCs’ introduction of a compact stateful path - yes, I said stateful 🌶️

— Whiteboard explanations of all relevant cryptographic subschemes, including FORS, WOTS+C, and XMSS

— Thorough discussion of the scheme’s tradeoffs and implications for Bitcoin’s existing functionality

If you have a vested interest in understanding what may be the future signature scheme protecting Bitcoin transactions in a post-quantum world, this episode is a must-watch.

WARNING: this episode is fairly technical — don't beat yourself up if you don't catch everything, or need to watch it a few times to grok the details.

This episode of Bitcoin Rails is brought to you by:

LayerTwo Labs @LayerTwoLabs — developing research, software, and technologies for scaling Bitcoin via the integration of Drivechains (BIP 300/301)

Hashi on @SuiNetwork — a primitive for executing Bitcoin DeFi transactions, without having to trust a federated bridge or other centralized entity

BitBox @BitBoxSwiss — an open-source Bitcoin-only hardware wallet, with smooth UX and no compromises on security. Check out Bitbox [dot] swiss and use code BITCOINRAILS to get a discount