SHRINCS BIP published: Quantum-secure Bitcoin comes with a catch

A recent Bitcoin Improvement Proposal (BIP) introduces a quantum-secure signature scheme called SHRINCS to upgrade Bitcoin's security against potential threats from advanced quantum computers. Blockstream co-founder, Adam Back, is leading the research into practical solutions to this issue, as he believes the technology's threat is decades away. SHRINCS is a hash-based post-quantum signature scheme that was initially tested on Blockstream's Liquid sidechain and has now been proposed as a BIP for Bitcoin.

However, SHRINCS isn't without its drawbacks. It's significantly larger than Bitcoin's existing ECDSA and Schnorr signatures, ranging from 548 to 4,619 bytes. That size increase could potentially slow down the blockchain to just 3 transactions per second, which is less than half of the current speed. Although Ethereum plans to address this issue by aggregating signatures using zero-knowledge proofs, Bitcoin's change would be more radical and face a steep uphill battle to gain support.

Blockstream is considering SHRINCS's size reduction as a potential solution, but it remains an early-stage and unaudited proposal. Despite the compromises, experts still view SHRINCS as the strongest contender for Bitcoin's post-quantum security without compromising its block economics.