Quantum Computer Breaks 15-Bit ECC Key, Threatening Bitcoin Security

On April 24, 2026, Giancarlo Lelli was awarded the Q-Day Prize by Project Eleven for successfully breaking a 15-bit elliptic curve key using publicly accessible quantum hardware, marking the largest public demonstration of a quantum attack on elliptic curve cryptography (ECC). This achievement raises concerns for Bitcoin, Ethereum, and over $2.5 trillion in ECC-secured digital assets, as it demonstrates a significant leap in quantum computing capabilities. Lelli's method utilized a variant of Shor's algorithm to derive a private key from its public counterpart across a space of 32,767 possibilities. While Bitcoin operates at a 256-bit scale, the gap between 15 bits and 256 bits is increasingly viewed as an engineering challenge rather than a fundamental barrier. The urgency for migration to post-quantum cryptography has intensified, especially following Google's commitment to achieving quantum security by 2029. Approximately 6.9 million Bitcoin are at risk due to their exposure through public keys on the blockchain. This event signifies a shift from theoretical risks to practical threats in the realm of quantum computing.

Key Points: • Giancarlo Lelli broke a 15-bit ECC key using quantum hardware, raising alarms for Bitcoin security. • The achievement represents a 512-fold increase in quantum attack capability since September 2025. • Approximately 6.9 million Bitcoin are vulnerable due to public key exposure on the blockchain.