Bitcoin developers unveil libshrincs, a proof-of-concept library for post-quantum security

Jonas Nick of Blockstream Research and collaborator remix7531 have released libshrincs, a proof-of-concept C library that implements a key component of a quantum-resistant signature scheme designed for Bitcoin. The library, announced on August 11 on Delving Bitcoin, represents one of the most rigorous attempts yet to formally verify cryptographic code meant to shield Bitcoin from the eventual arrival of powerful quantum computers. The project is notable not just for what it protects against, but for how it was built. The security and correctness proofs were largely generated with the help of large language models, including ChatGPT and Fable, under human oversight. What libshrincs actually does Libshrincs implements WOTS+C, the one-time signature component of a broader scheme called SHRINCS. SHRINCS, first proposed in December 2025, is a signature scheme that blends stateful and stateless hash-based signatures. The goal is to keep signature sizes compact enough to be practical for Bitcoin transactions while still providing quantum resistance. In stateful mode, signatures clock in at roughly 324 bytes. The scheme also includes a stateless fallback mechanism, essentially a safety net...