- Bitcoin uses different algorithms (ECDSA/SHA-256) than RSA, so faces no direct immediate threat from this specific quantum advance.
- Google’s May report estimates breaking a 2048-bit RSA key might now require fewer than 1 million physical qubits, down from 20 million.
Researchers at Shanghai University reported breaking a small RSA encryption key using quantum computing. They factored a 22-bit RSA key. This achievement demonstrates progress in applying quantum technology to cryptography, though current security standards remain intact.
RSA encryption protects sensitive data like financial transactions. It relies on the immense difficulty of factoring large numbers into prime numbers using traditional computers. The Shanghai team converted this factoring problem into a combinatorial optimization challenge. They solved it using a D-Wave Systems quantum annealing processor. This machine employed over 5,000 physical qubits – the basic units of quantum information.
The broken 22-bit key is much smaller than the 2,048-bit keys commonly used today. Therefore, existing RSA-based systems are not immediately threatened. The computational challenge scales exponentially with key size. However, the experiment signals progress towards methods that could one day threaten current encryption.
The relevance for Bitcoin is indirect
Bitcoin does not use RSA. It secures transactions and private keys using Elliptic Curve Digital Signature Algorithm (ECDSA) and the SHA-256 hash function. These systems rely on different mathematical problems than RSA.
Views on the timeline for a practical quantum threat vary. Adam Back, a Bitcoin developer and Blockstream founder, suggests practical danger might be “one or two decades away.” Other experts monitoring quantum progress warn the risk could materialize faster than expected.
A late May report from Google Quantum AI heightened broader concerns. Google researchers indicated that future quantum attacks could threaten not only RSA but also Elliptic Curve Diffie-Hellman (ECDH) encryption. ECDH shares mathematical foundations with Bitcoin’s ECDSA. Both depend on the difficulty of solving the elliptic curve discrete logarithm problem.
Google’s analysis suggests breaking a 2,048-bit RSA key might now require fewer than one million physical qubits. Previous estimates from 2019 suggested 20 million. This reduction stems from better algorithms and improved error correction techniques. Logical qubits, formed from many error-corrected physical qubits, are the functional units for such complex tasks.
This progress underscores a known risk: “harvest now, decrypt later” attacks. Adversaries could collect encrypted data today, hoping to decrypt it when sufficiently powerful quantum computers exist.
While Bitcoin’s specific algorithms aren’t broken, the underlying mathematical assumptions face a potential long-term challenge. The Shanghai experiment and Google’s analysis serve as reminders that crypto defenses must continue evolving.
