Time's Running Out for Bitcoin to Counter Quantum Computing Threat

Not all aspects of bitcoin are vulnerable to quantum computer attacks. The process of bitcoin mining, which utilizes a type of math known as hashing, is secure from quantum threats. The blockchain ledger and the rule that new bitcoins can only be created through mining would remain intact in the event of a quantum attack, allowing blocks to continue being produced and the chain to keep running. However, ownership would be compromised. Bitcoin wallets rely on a different type of math that converts a private key into a public address. This math is easily reversible in one direction but not the other, preventing unauthorized spending of coins. A quantum algorithm known as Shor's algorithm can collapse this gap, and a recent paper by Google demonstrated that such an attack could be executed with fewer resources than previously estimated. This article explores the potential risks, bitcoin's current measures, and whether the network can coordinate a significant security upgrade before quantum hardware becomes a threat. Approximately 6.9 million bitcoins, or one-third of all mined coins, are stored in wallets with publicly visible keys, making them vulnerable to quantum attacks. This includes early bitcoins and wallets that have been spent from, as spending reveals the key. Bitcoin's pseudonymous creator, Satoshi Nakamoto, holds around 1 million bitcoins that are also at risk. The 2021 Taproot upgrade inadvertently expanded the problem by publishing keys for remaining balances at addresses that have been spent from. While there are ongoing debates and proposals to address the quantum threat, bitcoin developers have yet to implement a concrete plan. In contrast, Ethereum has had a formal quantum-resistant program in place since 2018 and has made significant progress in migrating to quantum-safe math. Bitcoin's lack of a centralized authority and governance process makes it challenging to coordinate a network-wide upgrade. The biggest hurdle is deciding how to migrate the 6.9 million exposed coins, including whether to freeze old address formats, allow exposed coins to move to new quantum-safe addresses, or set a migration deadline. Each option has significant implications for bitcoin's character and stability. The recent Google paper highlights the urgency of adopting post-quantum cryptography, and the industry must decide whether to start now or wait until the threat becomes more apparent.