Declining Qubit Requirements Intensify Quantum Risk for Crypto

The quantum computing threshold needed to break blockchain encryption is falling rapidly, sharpening concerns that crypto networks may face security risks sooner than expected.

A new study from Caltech and quantum startup Oratomic estimates that a system with roughly 26,000 qubits could crack ECC-256—the elliptic curve cryptography securing Bitcoin and Ethereum—in about 10 days. More notably, the research suggests that as few as 10,000 physical qubits could be enough to compromise crypto wallets, a sharp reduction from earlier estimates that ran into the hundreds of thousands.

Qubits, the fundamental units of quantum computers, indicate system scale rather than speed and serve as a key benchmark for computational capability.

The findings, published on the arXiv preprint server, align with a separate Google Quantum AI paper that places the threshold for similar attacks below 500,000 qubits. Building on Google’s quantum circuit designs, the Oratomic team demonstrates that a neutral-atom approach—using laser-controlled atoms as qubits—could execute these attacks far more efficiently.

Together, the studies highlight a rapid shift in expectations. Estimates for running Shor’s algorithm, the quantum technique used to break public-key encryption, have fallen dramatically over the past two decades—from around one billion qubits to roughly 10,000.

Under these assumptions, a sufficiently advanced quantum machine could derive private keys from public addresses within days, potentially enabling attackers to access protected funds.

Traditional encryption appears more resilient by comparison. Breaking RSA-2048, widely used in financial systems, would require around 102,000 qubits and months of computation, making elliptic curve cryptography relatively more exposed due to its smaller key size.

While near-instant “on-spend” attacks remain unlikely in the short term, longer-term risks persist—particularly for funds held in older or reused wallet addresses, including millions of bitcoins that could be vulnerable.

The study carries important caveats. All nine authors have financial ties to Oratomic, with most employed by the company, positioning the research as both a technical contribution and a validation of its hardware approach.

Still, the broader trend is becoming increasingly clear. As the cost and scale required for quantum attacks continue to decline, the focus is shifting from whether crypto can be broken to whether the industry can upgrade its defenses in time.