How Quantum Computing Can Compromise Bitcoin Security in Under 10 Minutes

The first part of this series provided an overview of quantum computing, highlighting its distinction from classical computing. However, understanding the principles of quantum computing does not directly explain how it can be exploited to steal bitcoin. This requires insight into the security mechanisms of bitcoin and the specific weaknesses that quantum computers can exploit. This article commences with an examination of bitcoin's encryption method, known as elliptic curve cryptography, and progresses to discuss how a quantum algorithm can potentially breach this security, referencing the recent findings by Google. The security of bitcoin is based on a one-way function, where a private key is used to generate a public key, but reversing this process is virtually impossible for classical computers. This is due to the elliptic curve discrete logarithm problem, which becomes manageable with quantum computers through the application of Shor's algorithm. Shor's algorithm leverages the principles of superposition, entanglement, and interference to solve the discrete logarithm problem efficiently, thereby compromising the security of bitcoin. Despite Shor's algorithm being known for over 30 years, the implementation has been hindered by the requirement for a large number of stable qubits. Recent research by Google has significantly reduced the estimated number of qubits needed, from millions to fewer than 500,000, making the threat more tangible. The study designed quantum circuits that can run Shor's algorithm against bitcoin's elliptic curve, utilizing approximately 1,200 to 1,450 logical qubits. The process involves precomputing parts of the algorithm that depend on fixed, publicly known parameters of the elliptic curve, allowing the quantum computer to be in a primed state. Once a target public key is identified, the quantum computer can derive the private key within approximately nine minutes, which is close to the average block confirmation time of bitcoin. This timeline introduces a window of vulnerability for transactions. Moreover, a substantial portion of bitcoin, roughly one-third of the total supply, is stored in wallets with publicly exposed public keys, making them susceptible to attack without any time constraint. The implications of these findings and the advancing hardware capabilities will be explored in the next piece of this series.