New research from Google shows that quantum computers could require far less resources than previously thought to break the cryptography that secures cryptocurrency blockchains.
Google’s new research, released on Monday, estimates a quantum computer could crack the cryptography protecting Bitcoin (BTC) and Ethereum (ETH) using fewer than 500,000 physical qubits, based on its current assumptions about hardware capabilities. A qubit is the basic unit of a quantum computer.
The researchers compiled two quantum circuits to test on a superconducting-qubit, cryptographically relevant quantum computer (CRQC), reporting that it was a “20-fold reduction” in the number of qubits required to break the 256-bit elliptic curve discrete logarithm problem (ECDLP-256) widely used in cryptocurrency blockchains.
The research suggests that in a theoretical scenario, a quantum computer could crack a Bitcoin private key in as little as nine minutes, giving it a small window to perform an “on-spend attack” given Bitcoin’s 10-minute block time.
An “on-spend” quantum attack is a hypothetical future threat where a quantum computer is able to decipher a private key from a public key exposed during a transaction, allowing the attack to steal the funds.
“We should estimate the time required to launch an on-spend attack starting from this primed state at the moment the public key is learned to be roughly either 9 minutes or 12 minutes.”
“My confidence in Q-Day by 2032 has shot up significantly. IMO there’s at least a 10% chance that by 2032 a quantum computer recovers […] private key from an exposed public key,” said co-author and Ethereum researcher Justin Drake.
Graph showing the risk that an on-spend quantum attack that takes 9 minutes to derive a private key succeeds against Bitcoin. Source: Google Quantum AI
Ethereum is vulnerable to “at-rest attacks”
The researchers also warned that Ethereum’s account model is “structurally prone to at-rest attacks,” which means they don’t require timing.
An “at-rest” attack similarly uses a public key to derive a private key using a quantum computer,…
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