Blockstream researchers propose Bitcoin quantum fix without crowding out transactions

Researchers at Blockstream published a proposal on Thursday for SHRINCS. SHRINCS is a way to sign Bitcoin transactions that could withstand quantum computers without sharply reducing block transaction capacity. Bitcoin currently uses digital signatures based on elliptic-curve cryptography to prove control of coins without revealing private keys. A sufficiently powerful quantum computer running Shor's algorithm could eventually break that protection. The quantum computer could calculate a private key from a public key visible on the blockchain. An attacker could then forge a signature and spend the coins. The draft has no completed security proof. The reference software is not intended for production. The draft warns that moving certain keys between incompatible wallets can result in lost funds. Implementing the proposal would require a soft fork and network-wide agreement.