Quantum Attack Estimate Drops by Half, But Bitcoin and Ethereum Remain Vulnerable

A team of researchers from the Ethereum Foundation, Theta Labs, StarkWare, and other organizations has made a breakthrough in quantum computing, reducing the estimated computing resources needed to break the elliptic-curve cryptography protecting Bitcoin and Ethereum wallets by more than half. According to a paper published on arXiv, the new circuit requires 1,151 logical qubits and roughly 1.3 million Toffoli gates to perform one arithmetic step inside Shor's algorithm, the quantum routine that could eventually recover a private key from a public one. This is a significant improvement over the previous estimate of 3 billion, which was published by Google Quantum AI in March 2026.

The researchers used a hybrid workflow, combining human scientists with AI agents, to optimize the circuit and achieved an 86.1% reduction in the team's internal starting point. This approach could potentially compress the timeline for future resource-estimate papers. However, current machines are still far from reaching the required 1,151 stable logical qubits, let alone the additional qubits needed for the rest of the discrete-logarithm circuit.

The exposure of Bitcoin and Ethereum to quantum attacks is a growing concern, with an estimated 6.9 million BTC and 20.5 million ETH already exposed, according to Google Quantum AI's March 2026 whitepaper. The paper's authors note that the gap between 'theoretically weaker' and 'practically breakable' still spans years rather than months, but the industry still has time to migrate away from the cryptography used by both chains.