The Quantum Threat to Bitcoin: How a 9-Minute Window Can Steal Your Coins

Quantum computers are not just faster versions of regular computers, but a fundamentally different kind of machine that exploits the unique rules of physics at the atomic and particle level. To understand how a quantum computer can be used to steal bitcoin, it's essential to know what it's attacking and where the weakness lies. Bitcoin uses elliptic curve cryptography, which relies on a one-way map, making it easy to go forward but virtually impossible to reverse. However, a quantum algorithm called Shor's algorithm can break this one-way trapdoor, solving the discrete logarithm problem efficiently. This algorithm uses quantum properties such as superposition, entanglement, and interference to find the period of a function, which is crucial for breaking the encryption. Google's recent paper reduced the estimated number of qubits required to run Shor's algorithm, making it a more feasible threat. The paper also introduced a practical attack scenario, where a quantum computer can precompute parts of the algorithm and finish the calculation in about nine minutes, giving it a 41% chance of succeeding before a transaction is confirmed. This has significant implications for the security of bitcoin, particularly for the 6.9 million coins that have already had their public keys exposed on the blockchain.