The Quantum Threat to Bitcoin: How a Powerful Computer Can Steal Your Coins in Under 10 Minutes

The security of bitcoin relies on a complex mathematical system called elliptic curve cryptography, which is based on a one-way function that makes it easy to generate a public key from a private key, but extremely difficult to reverse the process. However, a quantum algorithm known as Shor's algorithm can potentially break this encryption, allowing an attacker to derive a private key from a public key. Recently, a paper by Google's Quantum AI division reduced the estimated number of qubits required to run Shor's algorithm against bitcoin's encryption from millions to fewer than 500,000. This reduction in qubit count introduces a practical attack scenario, where a quantum computer can be precomputed to wait for a target public key to appear, and then finish the calculation in approximately nine minutes. This time frame is alarming, as it is roughly the same as bitcoin's average block confirmation time, giving an attacker a 41% chance of deriving a private key and submitting a competing transaction before the original transaction confirms. Furthermore, approximately 6.9 million bitcoin are already vulnerable to an 'at-rest' attack, where a quantum computer can derive a private key from a public key that has already been exposed on the blockchain.