Security | April 2, 2026
Google Paper Maps Crypto's Quantum Weak Points
A new Google Quantum AI whitepaper cuts the estimated resources needed to break core crypto signatures and argues that Bitcoin, Ethereum, and tokenized assets should begin post-quantum migration now.
Google Quantum AI has published a whitepaper that moved the quantum deadline closer. The paper, dated March 30, says Shor's algorithm could break the secp256k1 elliptic-curve math used by bitcoin and ether with either 1,200 logical qubits and 90 million Toffoli gates or 1,450 logical qubits and 70 million Toffoli gates. Under the paper's superconducting-hardware assumptions, that translates to fewer than half a million physical qubits and a runtime measured in minutes.
It sorts quantum attacks into three buckets. "On-spend" attacks target a live transaction before it settles. "At-rest" attacks go after public keys that have already been exposed for long periods. "On-setup" attacks break a one-time protocol ceremony and leave behind a reusable backdoor. Google argues that fast-clock architectures such as superconducting, silicon, and photonic systems could eventually make on-spend attacks practical, while slower architectures may reach at-rest attacks first. The authors used a zero-knowledge proof to support the circuit claims without publishing the attack circuits themselves.