Quantum Computer Breaks 15-Digit ECC Key; Bitcoin's 256-Bit Security Remains Safe, Migration Countdown Accelerates

On April 25, Project Eleven awarded the Q-Day prize to researcher Giancarlo Lelli, who successfully derived a 15-digit elliptic curve private key from a public key using publicly accessible quantum hardware. This marks the largest-scale public demonstration of its kind to date, improving 512 times over the 6-digit demonstration in September 2025. Lelli employed a variant of Shor’s algorithm targeting the elliptic curve discrete logarithm problem, which is the mathematical foundation of Bitcoin’s signature scheme, using hardware with approximately 70 qubits. Currently, no known quantum computer can crack real Bitcoin wallets, and the 256-bit elliptic curve security of Bitcoin remains far beyond current quantum capabilities. Notably, Google lowered its resource estimates for ECDLP-256 on March 31 and set a quantum cryptography migration target for after 2029. Cloudflare followed suit, and the UK’s NCSC has also established migration milestones from 2028 to 2035. On-chain data indicates that approximately 6.93 million BTC are at potential quantum risk due to exposed public keys. The Bitcoin community has proposed BIP 360 and BIP 361 to promote the migration to quantum-resistant output types, but coordinating within a decentralized network remains the biggest challenge.