Independent researcher Giancarlo Lelli has successfully broken a 15-bit elliptic curve cryptography (ECC) key using publicly accessible quantum hardware, according to a report by Coin Edition.
The breakthrough occurred as part of a challenge hosted by Project Eleven, a startup that awarded Lelli a 1 BTC bounty through its Q-Day Prize program. The achievement marks the largest public break of its kind on quantum hardware to date.
Lelli recovered the private key from a public key across a search space of 32,767. He utilized a variant of Shor’s algorithm, a method designed to target the Elliptic Curve Discrete Logarithm Problem (ECDLP). This specific cryptographic vulnerability affects the digital signatures used to secure major blockchains including Bitcoin and Ethereum.
The widening gap between benchmarks and reality
While the 15-bit break is a significant milestone, the scale remains far below the requirements for modern encryption. Bitcoin utilizes 256-bit ECC to secure wallets, a complexity level vastly higher than the 15-bit test.
Lelli's result represents a 512-fold increase over a previous benchmark set in September 2025, when engineer Steve Tippeconnic broke a 6-bit key using IBM’s 133-qubit quantum computer. Project Eleven noted that while the gap between 15 bits and 256 bits is still wide, the distance is increasingly viewed as an engineering challenge rather than a fundamental limit of physics.
Recent research suggests the physical requirements for a full-scale attack may be lower than previously thought. A Google Research paper estimated that breaking 256-bit ECC could require fewer than 500,000 physical qubits. Conversely, a report from the California Institute of Technology and quantum startup Oratomic suggested the requirement could drop as low as 10,000 qubits.
Alex Pruden, chief executive of Project Eleven, stated that the resources needed for this type of quantum attack keep falling. He added that the barrier to running such an attack in practice is dropping, which increases the urgency for the industry to move toward post-quantum cryptography.
Project Eleven warned that approximately 6.9 million bitcoins are currently held in wallets with public keys visible on-chain, leaving them potentially exposed if sufficiently powerful quantum systems emerge. Several blockchain networks have already begun outlining migration paths, including Ethereum, Tron, StarkWare, and Ripple.
