StarkWare tests quantum-resistant Bitcoin transaction

StarkWare researcher Avihu Levy tested an experimental quantum-resistant Bitcoin transaction on the mainnet. StarkWare said the transaction demonstrated quantum-resistant spending without a fork. The transaction was confirmed Wednesday in Bitcoin block 964,199. It spent a 10,000-satoshi output protected by Levy's Quantum Safe Bitcoin scheme. MARA Pool mined the block after receiving the transaction through its Slipstream service. The scheme combines hash-based one-time signatures with computational searches that bind authorization to a specific transaction. The construction is intended to prevent forgery if a quantum computer breaks Bitcoin's elliptic-curve cryptography. The test moved Levy's April proposal from theory to an onchain demonstration. StarkWare said Bitcoin's existing consensus rules can accommodate this form of quantum-resistant spending without a protocol change. In March, Google researchers estimated that a capable quantum computer could derive a Bitcoin private key nine to 12 minutes after its public key becomes visible. Google said an attacker could then replace a pending transaction during Bitcoin's confirmation window. Levy introduced the Quantum Safe Bitcoin scheme in April. He estimated that generating a transaction would require $75 to $150 in GPU computation. Nathan Jeffay said the completed transaction cost about $150 to $200. StarkWare said the process required hours of computation. Levy's repository classifies these transactions as nonstandard under Bitcoin Core's default relay policies. StarkWare said ordinary nodes would not propagate the transaction before confirmation. The transaction therefore required direct submission through MARA's Slipstream service. The scheme applies to individual Bitcoin transactions rather than upgrading cryptography across the network. StarkWare CEO Eli Ben-Sasson said a soft fork should happen. Ben-Sasson said he believes a soft fork will happen. He said the scheme provides a safety net while protocol-level protections are developed. Bitcoin developers are separately considering BIP-360. The proposed soft fork would introduce a Pay-to-Merkle-Root output type. It would also remove Taproot's quantum-vulnerable key-path spend.