Quantum Breakthrough: 1 Bitcoin Prize Cracked on Public Quantum Computer – Is 'Q-Day' Closer Than We Think?

A researcher has used a publicly accessible quantum computer to crack a simplified version of a Bitcoin-style cryptographic key, marking the largest public demonstration of a quantum attack on elliptic curve cryptography to date.

Project Eleven awarded its 1 Bitcoin 'Q-Day Prize' bounty—currently worth nearly $78,000—to Italian researcher Giancarlo Lelli for breaking a 15-bit elliptic curve cryptography (ECC) key using a variant of Shor's algorithm.

The Significance

Elliptic curve cryptography underpins the digital signature schemes used by Bitcoin, Ethereum, and many other blockchains. While the 15-bit key in this demonstration is far smaller than the 256-bit cryptography securing real Bitcoin wallets, it represents another step toward the day when quantum computers pose a threat to hundreds of billions of dollars in cryptocurrency.

"We're still far, objectively, from the point at which you could actually break Bitcoin," Project Eleven CEO Alex Pruden told Decrypt. "But how long will it take to close that gap, and will we know the closer we get? I don't know that we will."

The Attack Details

The winning attack used a machine with about 70 qubits—quantum bits that can exist in multiple states at once—and ran in minutes once developed. The submission was reviewed by a panel of quantum researchers from academia and industry, including researchers from the University of Wisconsin–Madison and quantum software company qBraid.

The Road Ahead

Major quantum firms and research institutions are publishing increasingly aggressive hardware roadmaps. In March, Google publicly set a 2029 deadline to transition its systems to post-quantum cryptography. A Google research paper estimated that breaking Bitcoin could require fewer than 500,000 physical qubits, while a separate paper from Caltech and Oratomic estimated that number at 10,000 to 20,000 qubits using a neutral-atom architecture.

"Our own prediction for Q-Day is 2029 in the worst case," Pruden said. "I think that's because you really can't know with certainty how clever people are and how quickly these technological breakthroughs happen."

Vulnerable Bitcoin

Project Eleven said roughly 6.9 million Bitcoin are sitting in wallets with public keys visible on-chain that could become vulnerable if large-scale quantum computers emerge.

Industry Response

Bitcoin developers are currently weighing multiple proposals to address the threat. BIP-360 would introduce a quantum-resistant transaction format, while BIP-361 would phase out older signature schemes and eventually freeze coins that fail to migrate. Meanwhile, the Ethereum Foundation has formed a post-quantum security team, and co-founder Vitalik Buterin has outlined a roadmap to replace vulnerable parts of Ethereum's cryptography.

Pruden also pointed to advances in artificial intelligence as a factor that could push Q-Day closer by improving quantum error correction or helping attackers identify weaker cryptographic targets.

"A key part of quantum computing at scale is error correction," Pruden said. "AI can help make that process way more efficient."