Quick Take

• Researchers from several crypto projects have substantially reduced the estimated resource cost of a key operation involved in a potential quantum attack on Bitcoin and Ethereum.
• The resulting benchmark score is less than half Google’s previously reported level, though the researchers caution that the two approaches use different accounting methods.

A group of researchers has cut the estimated resources needed for a key operation involved in a potential quantum attack on Bitcoin and Ethereum. Their circuit requires 1,151 logical qubits and 1.30 million Toffoli gates, according to a technical paper authored by Theta Labs CTO Jieyi Long alongside researchers from several crypto projects and academic institutions.

The researchers measure the circuit's resource cost by combining the number of logical qubits it needs, which act as its working memory, with the number of Toffoli gates, the operations that account for much of its runtime. The two are multiplied into a single score, with a lower number indicating a more efficient circuit. Over roughly two months, submissions to a public challenge brought that score down 86%, from 10.75 billion to 1.496 billion. The final figure was also less than half Google's previously reported benchmark.

Google Quantum AI published its own estimates in March, setting a 2029 target for migration to post-quantum cryptography, but didn't release the circuit behind them. Alongside a zero-knowledge proof that a qualifying circuit existed, it did make a verifier public that could check other circuits and calculate their cost. Eigen Labs used that software to launch ECDSA.Fail on May 30, allowing researchers to submit improvements.

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