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

Quantum computers are not just faster versions of regular computers, but a fundamentally different kind of machine that exploits the principles of quantum mechanics. To understand how they can be used to steal bitcoin, we need to delve into the world of elliptic curve cryptography, which is the foundation of bitcoin's security. Every bitcoin wallet has a private key, which is a secret number, and a public key, which is derived from the private key using a mathematical operation. This one-way function is the basis of bitcoin's security, as it is easy to calculate the public key from the private key, but virtually impossible to do the reverse. However, a quantum algorithm known as Shor's algorithm can break this one-way function, and thus compromise the security of bitcoin. Shor's algorithm uses the principles of superposition, entanglement, and interference to find the private key, given the public key and the generator point. The recent paper by Google's Quantum AI division has reduced the estimated number of qubits required to run Shor's algorithm against bitcoin's elliptic curve, making the threat more imminent. The paper also introduced a practical attack scenario, where the quantum computer can precompute the parts of the algorithm that depend on the elliptic curve's fixed parameters, and then finish the calculation in about nine minutes once a target public key appears. This means that if a user broadcasts a transaction and their public key is visible in the mempool, a quantum attacker has roughly nine minutes to derive a private key and submit a competing transaction that redirects funds. The implications of this are alarming, especially considering that approximately 6.9 million bitcoin are already exposed and vulnerable to an 'at-rest' attack.