Blockstream's Quantum-Secure Bitcoin Solution SHRINCS Comes with a Catch

Blockstream, a company that specializes in blockchain and cryptocurrency research, has developed a post-quantum signature scheme called SHRINCS. According to Blockstream's CEO Adam Back, preparing for quantum threats is crucial, even though he believes the threat may not materialize for decades. The company's researchers have successfully implemented SHRINCS on its Liquid sidechain, and a Bitcoin Improvement Proposal (BIP) has been published.

SHRINCS is designed to be more efficient than other post-quantum signature schemes, which are significantly larger in size and could slow down the Bitcoin blockchain. Blockstream's researchers estimate that SHRINCS would allow the blockchain to run at 3 transactions per second (TPS), similar to its current speed.

However, there is a catch: SHRINCS is not yet cryptographically mature, and a security proof is still pending. Additionally, it introduces complexity to Bitcoin, as every signature uses a new one-time key, which can be stored on the user's device. If the device is lost or compromised, a large 'stateless fallback' transaction would be required to recover the keys.