How Quantum Computers Pose a Threat to Bitcoin Security in Under 10 Minutes

Quantum computers are distinct from regular computers, leveraging the unique rules of physics at the atomic and particle level. Understanding their functionality is crucial, but it doesn't directly reveal how they can be used to compromise bitcoin security. This requires insight into bitcoin's encryption and the vulnerabilities that quantum computers can exploit. Bitcoin employs elliptic curve cryptography, where each wallet has a private key and a public key derived from it through a mathematical operation on the secp256k1 curve. This process is akin to a one-way map, where starting from a known point, taking a certain number of steps leads to a public key, but reversing this process to find the private key is virtually impossible for classical computers. However, Shor's algorithm, a quantum algorithm discovered in 1994, can efficiently solve the discrete logarithm problem, breaking the encryption. The algorithm works by converting the problem into finding the period of a function, which quantum computers can solve efficiently by representing all possible inputs simultaneously and using the Fourier transform to find the correct answer. The recent Google paper reduced the estimated number of qubits needed to run Shor's algorithm against bitcoin's elliptic curve from millions to fewer than 500,000, significantly advancing the threat timeline. The paper also introduced a practical attack scenario where parts of the calculation can be precomputed, leaving only the final step to be completed once a target public key is identified. This final step can take approximately nine minutes, which is alarming given bitcoin's average block confirmation time of 10 minutes. It poses a significant risk, especially to the 6.9 million bitcoin with exposed public keys on the blockchain, which can be attacked without time constraints.