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

Understanding how a quantum computer works is not enough to comprehend its potential to steal bitcoin. To grasp this threat, it's essential to know how bitcoin's security operates and where its weaknesses lie. This article delves into bitcoin's encryption, explaining how it works and how a quantum algorithm can break it, with a focus on the recent findings by Google that significantly reduce the estimated time required for such an attack. Bitcoin relies on elliptic curve cryptography, which involves a one-way function that makes it easy to generate a public key from a private key but virtually impossible for classical computers to reverse the process. However, a quantum algorithm known as Shor's algorithm can efficiently solve this problem, potentially allowing an attacker to derive a private key from a public key. The algorithm leverages quantum properties such as superposition, entanglement, and interference to find the period of a function related to the elliptic curve, which is crucial for breaking the encryption. Despite Shor's algorithm being known for over 30 years, its application has been hindered by the requirement for a large number of stable qubits. Recent research by Google, in collaboration with other experts, has shown that the number of qubits needed could be significantly lower than previously thought, making the threat more feasible. The study also introduced a practical attack scenario where parts of the calculation can be precomputed, leaving only the final steps to be completed once a target public key is identified. This reduces the time required for the attack to approximately nine minutes, which is alarmingly close to the average block confirmation time in bitcoin. The implications are significant, with a substantial portion of bitcoin being potentially vulnerable to such attacks, especially those with publicly exposed public keys. The situation is further complicated by the existence of quantum computers that could potentially exploit these vulnerabilities in the near future.