Independent Researcher Breaks 15-Bit Elliptic Curve Key on Publicly Accessible Quantum Hardware, Wins Project Eleven's 1 BTC Q-Day Prize

Independent researcher Giancarlo Lelli won Project Eleven's 1 bitcoin Q-Day Prize worth approximately $78,000 on April 24, 2026, by breaking a 15-bit elliptic curve key using publicly accessible quantum hardware. The demonstration represents a 512-fold expansion from the previous 6-bit record set in September 2025 and marks the largest public quantum attack on Bitcoin-class cryptography achieved on commodity cloud hardware rather than national laboratory equipment. While Bitcoin uses 256-bit elliptic curve security, approximately 6.9 million bitcoin—one-third of total supply—sit in addresses with publicly visible keys potentially vulnerable to quantum attacks. The achievement comes as a March 2026 Google Research paper estimated full 256-bit attacks could require fewer than 500,000 physical qubits, prompting cryptocurrency projects including Bitcoin, Ethereum, Tron, StarkWare, and Ripple to develop post-quantum transition plans.

Breakthrough in quantum attack on elliptic curve cryptography

• ▪A Google Research paper in March 2026 estimated the cost of a full 256-bit elliptic curve attack at below 500,000 physical qubits
• ▪Giancarlo Lelli's 15-bit result expanded the previous 6-bit demonstration by a factor of 512 in seven months
• ▪Steve Tippeconnic performed a 6-bit elliptic curve key demonstration in September 2025 using IBM's 133-qubit quantum computer
• ▪Giancarlo Lelli's 15-bit elliptic curve key break was 512 times larger than the previous public demonstration in September 2025
• ▪The Project Eleven Q-Day Prize bounty was worth roughly $78,000 at the time of award
• ▪Lelli derived an elliptic-curve private key by attacking ECDLP underlying digital-signature schemes, not an encryption-key scheme
• ▪Project Eleven awarded its 1 bitcoin Q-Day Prize to Giancarlo Lelli on April 24, 2026
• ▪Independent researcher Giancarlo Lelli broke a 15-bit elliptic curve key on publicly accessible quantum hardware

Implications for Bitcoin and cryptocurrency security

• ▪A 15-bit elliptic curve key has a search space of 32,767 possibilities
• ▪Project Eleven estimates roughly 6.9 million bitcoin sit in addresses with publicly visible keys
• ▪Satoshi Nakamoto's estimated 1 million bitcoin have remained untouched since Bitcoin's earliest years

Industry response and quantum-resistant transition plans

• ▪Bitcoin developers have proposed BIP-360, a Bitcoin Improvement Proposal that would add quantum-safe address types

Perspective of Alex Pruden and Project Eleven

• ▪Alex Pruden emphasized that Giancarlo Lelli's achievement demonstrates quantum threats are no longer confined to theoretical research or classified facilities
• ▪Project Eleven designed the Q-Day Prize to incentivize public demonstrations of quantum computing capabilities against cryptocurrency cryptography

Perspective of Bitcoin and cryptocurrency developers

• ▪Bitcoin developers view BIP-360 as a necessary upgrade to protect the network against future quantum computing attacks

Perspective of Holders of bitcoin in addresses with exposed public keys

• ▪Satoshi Nakamoto's estimated 1 million bitcoin remain particularly vulnerable due to early address formats with exposed public keys and apparent wallet inactivity