Researchers cut quantum computing resources needed to attack Bitcoin and Ethereum by over 50%

Crypto researchers have optimized quantum circuits to reduce the resources needed to attack Bitcoin and Ethereum by over 50%, bringing the physical qubit requirement down to under 500,000. The breakthrough, achieved during the ECDSA.Fail challenge, targets the secp256k1 elliptic curve cryptography. While no current quantum computer can execute this attack, the findings expose vulnerabilities in legacy wallets holding 6.9 million BTC and 20.5 million ETH, prompting developers to accelerate post-quantum migration plans.

Quantum circuit optimization breakthrough

• ▪A research collaboration published a paper on March 30, 2026, detailing optimized quantum circuits that reduce the physical superconducting qubits needed to attack Bitcoin and Ethereum to fewer than 500,000, down from prior estimates of 9 million.
• ▪Researchers from the Ethereum Foundation, Theta Labs, StarkWare, and other organizations authored a technical paper detailing a quantum circuit that requires 1,151 logical qubits and 1.30 million Toffoli gates.
• ▪The newly designed quantum circuit scores approximately 1.5 billion in resource cost, representing a reduction of more than 50% compared to Google Quantum AI's benchmark of roughly 3 billion published in March 2026.
• ▪A separate study by researchers from Caltech and Oratomic explored neutral-atom architectures, claiming physical qubit requirements as low as 10,000 to 26,000 for similar computations, though execution would take days instead of minutes.

ECDSA.Fail challenge methodology

• ▪More than 100 participants, working alongside AI coding agents, spent roughly eight weeks submitting over 400 accepted designs to the ECDSA.Fail challenge, resulting in an 86% reduction in the circuit's resource score.
• ▪Eigen Labs launched the ECDSA.Fail open challenge on May 30, 2026, using a public verifier released by Google to allow researchers to submit and check improvements to quantum circuits.
• ▪During the ECDSA.Fail challenge, AI agents were heavily utilized for implementation, testing, and minor optimizations, while human researchers directed the research and made larger design changes.

Bitcoin cryptographic vulnerability

• ▪An 'on-spend' quantum attack could target Bitcoin transactions during the average 10-minute block confirmation window, with researchers estimating a 41% success probability of deriving the private key before confirmation.
• ▪An 'at-rest' quantum attack targets wallets with exposed public keys on the blockchain, which includes approximately 6.9 million BTC, with 1.7 million BTC of that total residing in legacy Satoshi-era P2PK outputs.
• ▪A quantum computer running Shor's algorithm targeting the secp256k1 elliptic curve could solve the 256-bit elliptic curve discrete logarithm problem (ECDLP-256) to derive private keys from exposed public keys.

Ethereum cryptographic vulnerability

• ▪Administrative keys controlling smart contracts for stablecoins and other tokenized assets govern around $200 billion in assets, representing a major vulnerability to quantum attacks on Ethereum.
• ▪Approximately 20.5 million ETH are stored in wallets with exposed public keys, making them vulnerable to potential 'at-rest' quantum attacks.

Post-quantum migration timeline

• ▪Google Quantum AI set a target of 2029 for migration to post-quantum cryptography, while Google's most advanced publicly known quantum processor, Willow, currently operates with 105 qubits.
• ▪The U.S. Commerce Department finalized CHIPS Act awards worth up to $100 million each for quantum computing firms Rigetti, D-Wave, and Quantinuum to build fault-tolerant quantum machines.
• ▪The Ethereum Foundation is targeting full post-quantum security across its execution, consensus, and data layers by December 2029.

Exposed wallet risk assessment

• ▪Wallets that have never broadcast a transaction remain safe from 'at-rest' quantum attacks, making the use of fresh addresses for every transaction an effective defensive measure.
• ▪Coinbase's Independent Advisory Board on Quantum Computing and Blockchain estimated in June 2026 that roughly 7 million BTC sit in addresses exposed to future quantum attacks due to address reuse and legacy formats.