New research suggests the cryptocurrency industry may have less time than anticipated to prepare for the risks posed by quantum computing, with potential implications for Bitcoin, Ethereum, and other major digital assets.
A whitepaper released on March 31 by researchers at Google indicates that breaking the cryptographic systems securing these networks may require fewer than 500,000 physical qubits on a superconducting quantum computer. This marks a sharp reduction from earlier estimates, which placed the requirement in the millions.
The study brings together contributors from both academia and industry, including Justin Drake of the Ethereum Foundation and Dan Boneh, alongside Google Quantum AI researchers led by Ryan Babbush and Hartmut Neven. The research was also shared with U.S. government agencies prior to publication, with input from organizations such as Coinbase and the Ethereum Foundation.
At present, no quantum system is capable of carrying out such an attack. Google’s most advanced processor, Willow, operates with 105 qubits. However, researchers warn that the gap between current hardware and attack-capable machines is narrowing. Drake has estimated at least a 10% probability that a quantum computer could extract a private key from a public key by 2032.
The concern centers on how cryptocurrencies are secured. Bitcoin relies on a mathematical problem known as the Elliptic Curve Discrete Logarithm Problem, which is considered practically unsolvable using classical computers. However, Peter Shor demonstrated that quantum algorithms could solve this problem far more efficiently, potentially allowing attackers to recover private keys, forge signatures, and access funds.
Importantly, this threat does not extend to Bitcoin mining, which relies on the SHA-256 algorithm. Experts suggest that using quantum computing to meaningfully disrupt mining remains decades away. Instead, the vulnerability lies in signature schemes such as ECDSA and Schnorr, both based on the secp256k1.
The research outlines three potential attack scenarios. “On-spend” attacks target transactions in progress, where an attacker could intercept a transaction, derive the private key, and submit a fraudulent replacement before confirmation. With Bitcoin’s average block time of 10 minutes, the study estimates such an attack could be executed in roughly nine minutes using optimized quantum systems, with parallel processing increasing success rates. Faster blockchains such as Ethereum and Solana offer narrower windows but are not entirely immune.
“At-rest” attacks focus on wallets with already exposed public keys, such as reused or inactive addresses, where attackers have significantly more time. A third category, “on-setup” attacks, involves exploiting protocol-level parameters. While Bitcoin appears resistant to this method, certain Ethereum features and privacy tools like Tornado Cash may face higher exposure.
Technically, the researchers developed quantum circuits requiring fewer than 1,500 logical qubits and tens of millions of computational operations, translating to under 500,000 physical qubits under current assumptions. This is a substantial improvement over earlier estimates, such as a 2023 study that suggested around 9 million qubits would be needed. More optimistic models could reduce this further, though they depend on hardware capabilities not yet demonstrated.
In an unusual move, the team did not publish the full attack design. Instead, they used a zero-knowledge proof generated through the SP1 zero-knowledge virtual machine to validate their findings without exposing sensitive details. This approach, rarely used in quantum research, allows independent verification while limiting misuse.
The findings arrive as both industry and governments begin preparing for a post-quantum future. The National Security Agency has called for quantum-resistant systems by 2030, while Google has set a 2029 target for transitioning its own infrastructure. Ethereum has been actively working toward similar goals, aiming for a full migration within the same timeframe. Bitcoin, however, faces slower progress due to its decentralized governance model, where major upgrades can take years to implement.
Early mitigation efforts are underway. A recent Bitcoin proposal introduces new address formats designed to obscure public keys and support future quantum-resistant signatures. However, a full transition away from current cryptographic systems has not yet been finalized.
For now, users are advised to take precautionary steps. Moving funds to new addresses, avoiding address reuse, and monitoring updates from wallet providers can reduce exposure, particularly for long-term holdings. While the threat is not immediate, researchers emphasize that preparation must begin well in advance, as advances in quantum computing continue to accelerate.
