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

Understanding how quantum computers work is one thing, but grasping how they can be used to steal bitcoin requires knowledge of what they are attacking and where the vulnerabilities lie. Bitcoin's security relies on elliptic curve cryptography, which uses a one-way function to derive a public key from a private key. This function is virtually impossible for classical computers to reverse, but a quantum algorithm known as Shor's algorithm can break it. Shor's algorithm exploits the properties of quantum mechanics to find the period of a function, which is essential for deriving the private key. Google's recent paper reduced the estimated number of qubits needed to run Shor's algorithm against bitcoin's elliptic curve, making the threat more realistic. The paper introduced a practical attack scenario where a quantum computer can precompute parts of the algorithm and then finish the calculation in about nine minutes once a target public key appears. This timeline is concerning because it is close to bitcoin's average block confirmation time, giving an attacker a significant chance of succeeding. The bigger concern is the large number of bitcoin that are already vulnerable to an 'at-rest' attack, where an attacker can take as long as needed to derive the private key.