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

The first part of this series delved into the physics behind quantum computing, but understanding how it works is only half the story. To grasp the threat it poses to bitcoin, we need to examine the target: the encryption that secures the cryptocurrency. Bitcoin relies on elliptic curve cryptography, a system that utilizes a pair of keys - a private key and a public key - to verify ownership and facilitate transactions. The private key is a secret number, while the public key is derived from it through a mathematical operation. This process is akin to a one-way map, where it's easy to move forward but virtually impossible to reverse the process using classical computers. However, the advent of quantum computers and algorithms like Shor's has changed the landscape. Shor's algorithm can efficiently solve the discrete logarithm problem, which is the backbone of bitcoin's security, by exploiting the principles of superposition, entanglement, and interference. The recent research by Google has significantly reduced the estimated number of qubits required to run Shor's algorithm against bitcoin's encryption, from millions to fewer than 500,000. This reduction, coupled with the possibility of precomputing parts of the algorithm, introduces a practical attack scenario where a quantum computer could derive a private key from a public key in approximately nine minutes. Given that bitcoin's average block confirmation time is 10 minutes, this poses a significant threat, especially to the 6.9 million bitcoin whose public keys have already been exposed on the blockchain. The implications of this vulnerability and the potential consequences for bitcoin's security are profound, making the development of quantum-resistant cryptography an urgent necessity.