Researchers have halved the estimated quantum attack complexity for Bitcoin and Ethereum, a significant breakthrough in cryptographic security.
A research team has made a significant breakthrough by reducing the computational complexity for a potential quantum attack on Bitcoin and Ethereum by over 50%, compared to previous estimates by Google. This finding, led by the CTO of Theta Network, was shared via social media.
Our very own CTO @jieyilong is the lead author on a paper that cuts the estimated quantum cost of the core operation in breaking Bitcoin and Ethereum's cryptography by more than half. https://t.co/2K3AzwuoBL
— Theta Network (@Theta_Network) September 10, 2026
More than 100 experts and AI agents collaborated on this research effort.
New Estimates Cut Quantum Requirements
The collaborative work involved specialists from the Ethereum Foundation, Theta Labs, StarkWare, and others, who developed a quantum circuit for a vital operation in Shor's algorithm. The circuit now requires 1,151 logical qubits and around 1.3 million Toffoli gates.
Originally estimated at approximately 3 billion conditional units by Google Quantum AI in March, the new calculation stands at about 1.5 billion, indicating a substantial decrease. However, researchers caution that comparisons may be flawed due to differing methodologies.
An alternative circuit design for practical Shor’s algorithm implementation yielded an estimate of around 1.96 billion conditional units.
AI's Role in Research Optimization
Optimization of the point addition operation on elliptic curves, frequently used in Shor's algorithm, was a key focus. This work was part of the ECDSA.Fail challenge organized by Eigen Labs, where over 100 contributors worked for eight weeks, implementing more than 400 improvements.
AI tools played a crucial role in coding, testing, and optimizing processes, while human participants guided the overall research direction. The impact of AI versus human contributions was not separately evaluated.
This development suggests that advancements in quantum attack preparations can stem not only from more powerful quantum computers but also from algorithmic and software improvements that lessen hardware demands.
Challenges Ahead for Quantum Attacks
Despite the promising findings, the research does not represent a full optimization of the attack. The newly developed circuit only addresses one key computational operation and does not incorporate physical error correction or the complete execution of Shor's algorithm. As a result, current systems remain secure against potential quantum threats.
Future designs could potentially lower the estimates further, with one suggesting an estimate of around 1.26 billion and another reducing logical qubit needs to 813, albeit at the cost of increased computations.
Bitcoin and Ethereum rely on the secp256k1 cryptographic scheme, which is vulnerable to quantum attacks. A sufficiently advanced quantum computer could exploit Shor's algorithm to derive private keys from public ones, enabling unauthorized transaction signing.
However, the researchers do not view an immediate quantum threat as likely, emphasizing that transitioning to quantum-resistant cryptography is a long-term challenge and that compromised keys cannot be retroactively secured. IonQ estimates that a fault-tolerant quantum computer with around 20,000 physical qubits would take 26 days to breach the secp256k1 cryptography.
