A quantum computing experiment has broken a 15-bit elliptic curve key, earning a 1 Bitcoin bounty worth over $78,000. The result matters because it extends the scale of demonstrated quantum attacks on cryptographic systems securing major blockchains.
Independent researcher Giancarlo Lelli achieved the result using a publicly accessible quantum computer, according to Project Eleven. The effort was part of its Q-Day Prize program, which incentivized breaking small elliptic curve keys between 1 and 25 bits.
How Close Are Quantum Systems To Breaking Crypto?
The attack used a variant of Shor’s algorithm to solve the Elliptic Curve Discrete Logarithm Problem, the mathematical foundation behind blockchain signatures. Lelli’s work expands on a prior 6-bit key break by Steve Tippeconnic in 2025, increasing the search space by a factor of 512.
— Steve Tippeconnic (@stevetipp) September 2, 2025
Yet the gap to real-world systems remains significant. Bitcoin relies on 256-bit elliptic curve cryptography, far beyond the 15-bit demonstration, though researchers increasingly view scaling as an engineering challenge rather than a theoretical barrier.
Estimates for breaking production-level cryptography vary widely. A recent Google Research paper suggested fewer than 500,000 physical qubits may be required, while research from California Institute of Technology and startup Oratomic proposed figures closer to 10,000 qubits.
Oratomic
“The resource requirements for this type of attack keep dropping,” said Alex Pruden, adding that the demonstration highlights urgency around post-quantum migration.
Project Eleven estimates roughly 6.9 million Bitcoin are held in wallets with exposed public keys, which could become vulnerable under sufficiently advanced systems.
Still, analysts caution against near-term alarm. Research firm Bernstein has characterized quantum risk as a medium- to long-term concern, noting that current hardware remains well below required thresholds for breaking production cryptography.
Can incremental advances like this accelerate timelines for quantum threats to blockchain security? The next catalyst will be whether further breakthroughs increase key sizes beyond experimental ranges and push post-quantum upgrades from planning into active deployment.
