Google study shows Bitcoin’s cryptography could fall in minutes, not decades

Google’s quantum researchers have significantly narrowed the resource gap between today’s quantum computers and the kind capable of breaking the cryptography that secures Bitcoin, Ethereum and most other blockchains — a finding that has reopened debate over how much time the digital-asset industry actually has to prepare.

In a whitepaper published by Google Quantum AI, in collaboration with researchers from the Ethereum Foundation and Stanford University, the team presented new resource estimates for breaking the 256-bit Elliptic Curve Discrete Logarithm Problem (ECDLP-256) — the mathematical problem underlying the secp256k1 curve that protects nearly every major cryptocurrency’s private keys.

The paper’s authors, led by Ryan Babbush and Hartmut Neven of Google Quantum AI, said an optimised version of Shor’s algorithm could solve the problem using either fewer than 1,200 logical qubits and 90 million Toffoli gates, or fewer than 1,450 logical qubits and 70 million Toffoli gates — whichever pairing reflects a trade-off between qubit count and gate operations.

On error-corrected superconducting hardware, the researchers estimated this could translate into an attack completed in minutes using fewer than half a million physical qubits.