Blockstream Publishes SHRINCS BIP: Quantum-Secure Bitcoin Solution with a Catch

Blockstream's SHRINCS BIP has been published, providing a quantum-secure solution for Bitcoin. According to Blockstream co-founder and CEO Adam Back, the safe thing is to prepare for the threat well in advance, despite his skepticism about the technology's maturity.

The proposed scheme, SHRINCS, is a hash-based post-quantum signature that has been tested in production on Liquid sidechain. It has a minimum size of 548 bytes and can grow as large as 4,619 bytes, but is still smaller than most post-quantum signatures. The blockchain's speed could run at 3 TPS with SHRINCS.

However, the proposal also introduces additional complexity to Bitcoin and relies on statefulness, which can be a potential fragility. Marin Ivezic, author of PostQuantum.com, notes that while SHRINCS is a strong contender for post-quantum security without wrecking Bitcoin's block economics, it has not been audited and lacks the years of public cryptanalysis that NIST signatures have weathered.

Blockstream is continuing to research and optimize the scheme, with plans to refine SHRINCS and add a companion scheme called SHRIMPS. The company is also considering lattice-based signature schemes and ZK proof aggregation of signatures, which could potentially double Bitcoin's speed to 6.7 TPS.