Benedikt Bünz

Zero-Knowledge Proofs For Post-Quantum Bitcoin | BENEDIKT BÜNZ

- Zero-knowledge proofs (ZKPs) have historically been dismissed by Bitcoin developers due to trusted setups and inefficiency, but the newest generation of hash-based proofs eliminates these concerns and may become essential for post-quantum security. - Hash-based signatures are the preferred first step for Bitcoin's post-quantum transition because they minimize new cryptographic assumptions (built from SHA-256) and have maximum proven security, though they produce signatures 20x larger than current ECDSA signatures. - Stateful hash-based signature schemes like SPHINCS+ and hybrid approaches such as Shrinks (with fallback recovery mechanisms) balance signature size against practical deployment challenges in cold-storage custody. - Zero-knowledge proofs enable **signature batching** to compress post-quantum signatures in blocks: miners can produce a single small proof (~200 kilobytes) asserting validity of thousands of hash-based signatures, making blocks feasible despite signature size inflation. - Benedikt Bünz and Dan Boneh are leading a new post-quantum cryptography unit at localhost research to advance hash-based signatures, threshold schemes, and ZKP integration for Bitcoin specifically. - Lattice-based signatures offer shorter signatures and richer functionality (threshold, adapter) but face political resistance in Bitcoin due to higher mathematical complexity and structure; a two-step upgrade (hash-based first, lattices later) may be necessary.