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

In the first part of this series, we delved into the physics behind quantum computing. Now, we're going to discuss the potential target of a quantum attack: Bitcoin's encryption. To understand how a quantum computer can be used to steal Bitcoin, we need to grasp how Bitcoin's security works and where its weaknesses lie. This starts with elliptic curve cryptography, a system used to prove ownership of Bitcoin. Each wallet has two keys: a private key, which is a secret number, and a public key, derived from the private key through a mathematical operation. The relationship between the private and public keys is like a one-way map, where it's easy to go forward but virtually impossible to go backward using classical computers. However, a quantum algorithm known as Shor's algorithm can break this one-way trapdoor, solving the elliptic curve discrete logarithm problem efficiently. This algorithm relies on quantum properties such as superposition, entanglement, and interference to find the period of a function, which ultimately reveals the private key. The recent Google paper introduced a practical attack scenario, reducing the estimated number of qubits needed to launch a successful attack and introducing the concept of a 'nine-minute window' during which a quantum attacker could derive a private key and submit a competing transaction. This has significant implications for Bitcoin's security, particularly for the 6.9 million Bitcoin already exposed on the blockchain.