Researchers Cut the Estimated Quantum Cost of a Key Step in Attacking Bitcoin and Ethereum by More Than Half

A crowdsourced challenge of more than 100 researchers and AI agents drove a quantum benchmark down 86% in two months, well below Google’s March figure.

Bitcoin's quantum clock just moved up again

Posted September 11, 2026 at 6:45 am EST.

An open challenge to optimize one component of a quantum attack on Bitcoin and Ethereum has produced a circuit far cheaper than the best figure previously reported. A paper published on arXiv Thursday describes a point-addition circuit for secp256k1, the elliptic curve both networks use, that needs 1,151 logical qubits and about 1.30 million Toffoli gates.

The benchmark multiplies qubits by gates into a single spacetime score, where lower is better. Over roughly two months of submissions, that score fell 86%, from 10.75 billion to about 1.496 billion, which is more than 50% below the result Google Quantum AI reported in March. One of the paper’s authors Theta technology chief Jieyi Long, however, cautioned against wholly taking the result of the challenge as superior to Google’s findings, citing differences in interfaces and accounting conventions.

Point addition is repeated many times inside Shor’s algorithm, which a fault-tolerant quantum computer could use to recover a private key from a public key already exposed onchain. Cheaper circuits do not build that machine, and the authors stress this is not an attack, but they shrink the margin holders are working with: Coinbase‘s quantum advisory board estimated in June that roughly 7 million BTC sit in addresses with visible public keys.