A new study by Google Quantum AI has revealed that future quantum computers may be capable of breaking the encryption that secures Bitcoin, Ethereum, and most cryptocurrencies using far fewer resources than previously believed.

The research paper, “Securing Elliptic Curve Cryptocurrencies against Quantum Vulnerabilities: Resource Estimates and Mitigations,” was released on March 30, 2026 by scientists from Google Quantum AI, the University of California Berkeley, Stanford University, and the Ethereum Foundation.

Quantum Threat Comes Into Focus

Bitcoin and Ethereum rely on elliptic curve cryptography to protect users’ private keys and digital assets. For years, experts believed that cracking this encryption would require extremely powerful quantum machines far beyond current technology.

However, the new study shows that a quantum attack could theoretically be carried out using around 1,200 logical qubits, a major reduction from earlier estimates that assumed millions would be necessary.

Researchers calculated that such an attack could run on future quantum systems using fewer than 500,000 physical qubits operating with low error rates; a kind of hardware that does not yet exist but is now considered achievable in the long term.

How a Quantum Crypto Attack Could Work

The paper highlights a potential vulnerability during crypto transactions.

When a Bitcoin or Ethereum transaction is broadcast to the network, the user’s public key becomes temporarily visible in the transaction pool, known as the mempool. A sufficiently advanced quantum computer could theoretically analyze that public key and derive the corresponding private key before the transaction is confirmed.

This type of attack, called an “on-spend” attack, could allow funds to be redirected in real time.

To prevent misuse, researchers validated their findings using zero-knowledge proofs and did not publish the executable attack code.