Quantum Bitcoin Attack Costs Drop Over 50%

Researchers have significantly reduced the estimated quantum computing resources needed for a key calculation that could eventually threaten Bitcoin and Ethereum cryptography, according to a new study involving researchers from the Ethereum Foundation, Theta Labs, StarkWare and other organizations.

The paper outlines a quantum circuit requiring 1,151 logical qubits and roughly 1.3 million Toffoli gates. Its combined resource score is approximately 1.5 billion, more than 50% below the roughly 3 billion benchmark published by Google Quantum AI in March. Researchers cautioned that the comparison is not exact because the two designs use different interfaces and accounting methods.

Another version designed to more closely reflect how Shor's algorithm would perform the calculation achieved a score of about 1.96 billion, also below Google's previous estimate.

The research focuses on optimizing point addition, a calculation repeatedly used within Shor's algorithm. A sufficiently powerful quantum computer running Shor's algorithm could theoretically derive a private key from an exposed public key, potentially allowing an attacker to authorize cryptocurrency transactions. Both Bitcoin and Ethereum rely on secp256k1 cryptography, making the findings relevant to their long-term security.

More than 100 participants worked with AI coding agents for roughly eight weeks through ECDSA.Fail, an open challenge created by Eigen Labs. The project generated more than 400 accepted submissions. AI agents were primarily used for coding, testing and incremental optimization, while human researchers generally directed broader research strategies and major design changes.

However, the findings do not mean Bitcoin or Ethereum can currently be cracked by quantum computers. The circuit addresses only one major component of a potential attack and excludes physical error correction, the complete Shor algorithm and various hardware-specific costs.

Resource requirements are also continuing to decline. While the headline result reflects a July cutoff, a later design reduced the score to approximately 1.26 billion. Another lowered the requirement to 813 logical qubits, although with substantially greater computational demands.

Lead author and Theta Labs CTO Jieyi Long said an attack is not imminent, but preparations are important because migrating blockchain networks to quantum-resistant cryptography could take years.

The research comes as the U.S. Commerce Department finalized CHIPS Act awards of up to $100 million each for Rigetti, D-Wave and Quantinuum, supporting development of more advanced quantum computing hardware.