The Threat of Quantum Computing to Bitcoin Security

Quantum computers are fundamentally different from regular computers, exploiting the unique rules of physics at the atomic and particle level. Understanding how they work is crucial to grasping the potential threat to bitcoin's security. Bitcoin's encryption relies on elliptic curve cryptography, which uses a one-way map to derive a public key from a private key. This map is virtually impossible for classical computers to reverse, but a quantum algorithm known as Shor's algorithm can break it. The algorithm uses the principles of superposition, entanglement, and interference to find the period of a function, which is essential to deriving the private key. Google's recent paper reduced the estimated number of qubits required to run Shor's algorithm, making the threat more feasible. The paper also introduced a practical attack scenario, where a quantum computer can precompute parts of the algorithm and finish the calculation in approximately nine minutes. This time frame is alarming, as it is close to bitcoin's average block confirmation time, giving an attacker a roughly 41% chance of succeeding. The bigger concern is the 6.9 million bitcoin already exposed on the blockchain, which are vulnerable to an 'at-rest' attack that requires no time constraint.