Independent researcher Giancarlo Lelli calculated a 15-bit cryptographic key on ECC using a publicly accessible quantum computer, as reported by the startup team Project Eleven.
Project Eleven Awards 1 BTC Q-Day Prize for Largest Quantum Attack on Elliptic Curve Cryptography to Date
Researcher breaks 15-bit ECC key on publicly accessible quantum hardware in a 512x jump from the previous public demonstration.
Project Eleven today awarded the Q-Day…
— Project Eleven (@projecteleven) April 24, 2026
Lelli applied a modification of Shor’s algorithm to a search space of 32,767 combinations. This method targets the discrete logarithm problem on elliptic curves, the mathematical foundation of digital signatures used in most blockchains.
Project Eleven awarded the researcher 1 BTC as part of the Q-Day Prize program. The initiative was launched in 2025 to crack keys ranging from 1 to 25 bits.
In September, engineer Steve Tippeconnic extracted a six-bit ECC key on a 133-qubit IBM computer. Developers noted that this was the first public attack of its kind on quantum hardware.
Lelli’s result surpassed it by 512 times. The project team described the latest experiment as the largest quantum-based attack on elliptic curves to date.
The scale of the demonstration is still incomparable to real systems: Bitcoin uses 256-bit ECC for wallet protection. Project Eleven noted the gap. However, programmers consider the transition more of an engineering challenge than a fundamental physical problem.
Preparation Needed
CEO of Project Eleven Alex Pruden stated that the resource requirements for such attacks are decreasing, and the barrier to their practical implementation is gradually lowering. According to him, this underscores the need to transition to post-quantum cryptography.
The company also pointed out that about 6.9 million BTC are held in addresses where public keys are already visible on-chain. Should sufficiently powerful quantum systems emerge, such wallets could become the most vulnerable.
In recent months, discussions about quantum risks to the crypto market have intensified. Earlier, Google researchers reduced the estimate of quantum power needed to break Bitcoin. However, some believe the issue is exaggerated.
Back in April, Bitcoin developer Jameson Lopp and a group of experts presented a draft proposal BIP-361. The initiative suggests freezing coins vulnerable to quantum computers.
The community criticized the idea, calling it authoritarian and confiscatory.
Other blockchains have also begun preparing for a transition to post-quantum cryptography, including Ethereum and Ripple.