Bitcoin, Ethereum Quantum Threat Falls 50% in New Research Assessment

New research suggests that the computational requirements for a future quantum attack on Bitcoin and Ethereum could be significantly lower than previously estimated, after researchers and AI coding agents improved a key calculation used in Shor’s algorithm.

The study, shared with CoinDesk, reduced the estimated workload for the calculation by more than 50% compared with a Google Quantum AI benchmark published in March. Researchers involved in the project came from the Ethereum Foundation, Theta Labs, StarkWare and other organizations.

Their primary quantum circuit requires 1,151 logical qubits and approximately 1.3 million Toffoli gates. Logical qubits provide an indication of the size of the quantum computer needed, while Toffoli gates represent the computational work that machine would have to perform.

The resulting score was around 1.5 billion, substantially below Google Quantum AI’s March figure of roughly 3 billion. The researchers noted, however, that the comparison is not perfectly equivalent because the two studies use different interfaces and accounting approaches.

Another version of the circuit, designed to more closely correspond to its eventual role in Shor’s algorithm, produced a score of approximately 1.96 billion. That figure also remained below Google’s benchmark.

Optimizing a key cryptographic operation

The researchers concentrated on point addition, a mathematical operation that Shor’s algorithm must perform repeatedly.

This matters for cryptocurrencies because a sufficiently capable quantum computer could potentially use Shor’s algorithm to derive a private key from an exposed public key. An attacker could then theoretically generate valid signatures and authorize transactions from the affected wallet.

Bitcoin and Ethereum are both based on secp256k1, the elliptic-curve cryptography targeted by the research.

The optimization effort brought together more than 100 participants over about eight weeks through ECDSA.Fail, an open research challenge created by Eigen Labs. More than 400 submissions were accepted, with successful improvements becoming starting points for additional rounds of optimization.

AI agents were used extensively to implement changes, run repeated tests and identify smaller optimizations. Human researchers remained responsible for selecting broader research directions and making larger design decisions.

The paper does not distinguish precisely how much of the final improvement can be attributed to humans versus AI.

Still, the results demonstrate why advances in algorithms could affect the quantum threat timeline even if quantum hardware itself does not rapidly improve. More efficient circuits can reduce the size and computational capacity required from a future quantum machine.

No quantum computer can break crypto today

The findings do not indicate that Bitcoin or Ethereum are currently vulnerable to quantum attacks.

The researchers addressed only one major component of a potential Shor-based attack. Their work does not account for physical error correction, the complete Shor computation or certain costs that would arise from running the circuit on real quantum hardware.

No existing quantum machine is capable of breaking Bitcoin or Ethereum using the techniques described in the research.

Optimization has continued beyond the paper’s July cutoff. A later design brought the score down to about 1.26 billion, while another approach reduced the required machine size to 813 logical qubits but at the cost of substantially more computation.

Jieyi Long, the study’s lead author and CTO of Theta Labs, told CoinDesk that the results should not be viewed as evidence that a quantum attack is about to happen. The concern is the amount of preparation required to protect blockchain networks, since developing and deploying a replacement for vulnerable cryptography could take years and cannot be done retroactively.

Meanwhile, governments are investing in the hardware that could eventually make large-scale quantum computing practical. The U.S. Commerce Department this week finalized CHIPS Act awards worth up to $100 million each for Rigetti, D-Wave and Quantinuum, while taking minority stakes in the three companies. The funding is intended to support the development of larger fault-tolerant quantum systems.

For Bitcoin and Ethereum, the research adds to a growing reason to begin preparing for quantum-resistant cryptography before a practical attack becomes possible. The threat remains theoretical today, but falling computational requirements show that improvements in algorithms could be just as important as advances in quantum hardware.