How Quantum Computing Threatens Bitcoin Security in Under 10 Minutes

Quantum computers are fundamentally different from regular computers, leveraging the unique rules of physics at the atomic and particle level. Understanding how they work is crucial to grasping how they can be used to compromise bitcoin security. Bitcoin relies on elliptic curve cryptography, a system that uses a private key and a public key derived from it through a mathematical operation on a specific curve. This one-way function allows for easy verification of ownership but makes it virtually impossible for classical computers to reverse-engineer the private key from the public key. However, Shor's algorithm, a quantum algorithm discovered in 1994, can efficiently solve the discrete logarithm problem, breaking the security of bitcoin's encryption. The algorithm utilizes the principles of superposition, entanglement, and interference to find the period of a function, which is key to deriving the private key. Google's recent paper has significantly reduced the estimated number of qubits needed to run Shor's algorithm against bitcoin's elliptic curve, from millions to fewer than 500,000, and introduced a practical attack scenario where parts of the calculation can be precomputed. This reduces the time needed to derive a private key once a public key is exposed to approximately nine minutes, which is close to bitcoin's average block confirmation time. The implications are alarming, with about 6.9 million bitcoin potentially vulnerable to an 'at-rest' attack once a sufficiently powerful quantum computer is built.