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

To understand how a quantum computer can be used to steal bitcoin, it's essential to know how bitcoin's security is built and where the weakness lies. Bitcoin uses elliptic curve cryptography, which involves a one-way map that makes it easy to go forward but virtually impossible for classical computers to reverse. However, a quantum algorithm known as Shor's algorithm can break this one-way trapdoor. The algorithm solves the discrete logarithm problem efficiently, which would take a classical computer an impractically long time to solve. Shor's algorithm uses the principles of superposition, entanglement, and interference to find the period of a function, which is crucial in breaking the encryption. Although Shor's algorithm has been known for over 30 years, running it requires a quantum computer with a large enough number of stable qubits. Google's recent paper reduced the estimated number of required qubits, making the threat more pressing. The paper introduced a practical attack scenario where the quantum computer can precompute parts of the algorithm and finish the calculation in about nine minutes once a target public key appears. This timing is alarming because it gives the attacker a significant chance of succeeding before the original transaction confirms. Moreover, approximately 6.9 million bitcoin are already vulnerable to an 'at-rest' attack, which does not require a race against the clock. The implications of this quantum threat and the potential consequences for bitcoin's security are significant and warrant further exploration.