Today, we're publishing BIP SHRINCS, the first concrete proposal for a post-quantum signature scheme designed specifically for Bitcoin. The BIP draft turns what began as a rough idea into exact algorithms with an executable reference implementation. This is an important milestone: the discussion can now focus on analyzing, criticizing, and improving a concrete proposal. The BIP makes choices ranging from major design questions, such as whether to support flexible XMSS and how to balance signature size against verification time, to the many smaller decisions involved in saving a byte here or there. All of these choices are up for debate. Big thanks to Mike Casey, @conduition, @Ethan_Heilman, @kudinov_mikhail, @olkurbatov, Boris Nagaev, and @remix7531 for their contributions to the BIP. A lot more work lies ahead: - The draft BIP specifies only the cryptography. Using SHRINCS in Bitcoin Script will require a separate BIP. - We are working on a security proof for the exact construction and parameters. - Wallet integration and user experience, for example around backups and recovery after state loss, are still at an early stage. The design space remains wide open. SHRINCS is not intended to be Bitcoin's "final" signature scheme, and it is not optimal along every axis. I do think it is a very good trade-off among the options we have now. bitcoin-dev post: groups.google.com/g/bitcoind… Draft BIP: github.com/SHRINCS/shrincs-b…