Blockstream Publishes BIP for SHRINCS Quantum-Resistant Signatures
Blockstream has published a Bitcoin Improvement Proposal for SHRINCS, a post-quantum signature scheme the company describes as the first concrete proposal designed specifically for Bitcoin, according to Cointelegraph.
Blockstream Research’s Jonas Nick called SHRINCS not intended to be Bitcoin’s final signature scheme but said it represents a strong tradeoff among currently available options. The scheme was unveiled by Nick and Mikhail Kudinov in December 2025, with an opcode proposal published in May and the full BIP released this week, per Cointelegraph.
Scientists broadly agree that sufficiently advanced quantum computers could eventually reverse-engineer private keys from public keys, threatening Bitcoin’s security model. Post-quantum signature schemes endorsed by the National Institute of Standards and Technology are between 38 and 123 times larger than Bitcoin’s existing ECDSA and Schnorr signatures, a size increase that could slow the network to a fraction of one transaction per second, Cointelegraph reported.
SHRINCS, by contrast, has a minimum size of 548 bytes plus a 48-byte public key and can grow up to 4,619 bytes, roughly nine times larger than existing Schnorr signatures. Because Bitcoin’s Segregated Witness structure discounts witness data, this would still allow the network to process about 3 transactions per second, close to current throughput, according to estimates cited by Cointelegraph. Comparable NIST-approved lattice and hash-based schemes would reduce throughput to 0.5 and 0.36 TPS, respectively.
Marin Ivezic, founder of Applied Quantum and author of PostQuantum.com, told Cointelegraph’s Magazine that SHRINCS is the most Bitcoin-native post-quantum design produced so far, citing its compatibility with BIP-39 seed recovery and reliance on SHA-256 assumptions already used in Bitcoin mining. He cautioned the scheme remains unaudited and has not undergone the years of public cryptanalysis NIST-approved signatures have received.
SHRINCS was tested on Blockstream’s Liquid sidechain in March. The BIP itself notes that a full security proof is still pending.
Based on reporting by cointelegraph.com.
