Here’s what ‘cracking’ bitcoin in 9 minutes by quantum computers actually means
Google’s quantum paper made headlines with that number. Here’s what it means, what’s actually at risk, and why 6.9 million bitcoin are more exposed than the rest.
What to know:
- New research from Google’s Quantum AI team suggests a future quantum computer could derive a bitcoin private key from a public key in about nine minutes, potentially allowing attackers to hijack transactions before they are confirmed.
- Roughly one-third of all bitcoin, including early coins and any held in addresses whose public keys have been exposed or reused, could be stolen at leisure by a sufficiently powerful quantum computer without the time pressure of a live transaction.
- While bitcoin’s core mining process would continue to function, the ability to derive private keys from public keys would undermine the network’s ownership guarantees, and unlike Ethereum, bitcoin has not yet begun migrating to post-quantum cryptography.
Let’s start with how bitcoin transactions work. When you send bitcoin, your wallet signs the transaction with a private key, a secret number that proves you own the coins.
That signature also reveals your public key, a shareable address, which gets broadcast to the network and sits in a waiting area called the mempool until a miner includes it in a block. On average, that confirmation takes about 10 minutes.
Your private key and public key are linked by a math problem called the elliptic curve discrete logarithm problem. Classical computers can’t reverse that math in any useful timeframe, while a sufficiently powerful future quantum computer running an algorithm called Shor’s could.
Here’s where the nine minutes part comes in. Google’s paper found that a quantum computer could be “primed” in advance by pre-computing the parts of the attack that don’t depend on any specific public key.
