GOOGLE researchers say breaking the cryptographic foundations of most major cryptocurrencies is far nearer than previously believed, with estimates showing a 20-fold reduction in quantum resource requirements. They designed quantum circuits capable of breaking the 256-bit elliptic curve discrete logarithm problem (ECDLP-256) used by Bitcoin, Ethereum and other blockchains, using fewer than 1,200 logical qubits and around 90 million Toffoli gate operations.
The team asserts the attack could be executed in minutes on a machine with fewer than 500,000 physical qubits, down from about 10 million, though such hardware remains out of reach today. The findings come as Google moved up its timeline for transitioning to post-quantum cryptography, with a target of 2029. Notably, Google did not publish the actual quantum circuits, instead releasing a zero-knowledge proof to allow independent verification of the claims without disclosing reproducible details. Published on 31 March 2026.