Time Is Running Out for Bitcoin to Mitigate Quantum Computing Threat

Not all aspects of bitcoin are vulnerable to quantum computers. The process of mining, which involves adding new blocks to the blockchain, utilizes a type of mathematics called hashing that is resistant to quantum computing. As a result, the blockchain itself and the rule that new bitcoins can only be created through mining would remain intact in the event of a quantum attack. However, ownership of bitcoins is a different story. Bitcoin wallets rely on a specific type of mathematics that converts a private key into a public address. This math works seamlessly in one direction but is extremely difficult to reverse, which is what prevents unauthorized individuals from spending someone else's coins. A quantum algorithm known as Shor's algorithm can bypass this one-way math problem. A recent paper by Google demonstrated that this attack could be executed with far fewer resources than previously thought, and within a timeframe that competes with bitcoin's block times. This article, the final installment in a series, explores the potential consequences and the response from the bitcoin community. Approximately 6.9 million bitcoins, roughly one-third of all mined bitcoins, are stored in wallets whose public keys are already visible on the blockchain. These coins are at risk of being stolen by a quantum attacker. The attacker wouldn't need to rush; they could systematically work through the wallets with exposed keys at their leisure. This includes the roughly 1 million bitcoins held by bitcoin's pseudonymous creator, Satoshi Nakamoto, which have remained untouched since the network's early days. The 2021 Taproot upgrade inadvertently expanded the problem by making any bitcoin spent since its activation publish the key protecting the remaining balance at that address. While there is ongoing debate and some proposed solutions, nothing concrete has emerged from bitcoin developers yet. In contrast, Ethereum has had a formal quantum-resistant program in place since 2018 and is actively working on migrating its security to quantum-resistant mathematics. Bitcoin has no equivalent strategy, although there are some formal proposals, such as BIP-360, which suggests adding new quantum-safe address types, and a proposal from BitMEX Research for a detection system to trigger defensive actions in case of a quantum attack. However, neither proposal has broad support from bitcoin's core developers, and they address different parts of the problem. The lack of urgency and coordination among bitcoin developers is a significant challenge. Bitcoin's development culture is based on decentralization and resistance to central authority, which has kept the network stable but makes implementing changes, including those necessary to mitigate quantum threats, more difficult. The migration of the 6.9 million exposed coins requires decisions that the network has historically avoided, such as freezing old address formats or allowing exposed coins to move to new quantum-safe addresses. Each option has significant implications for the character of the bitcoin network. The future of bitcoin's security in the face of quantum computing threats remains uncertain, with the question being whether the network can coordinate a significant security upgrade before quantum computers become capable of exploiting the current vulnerabilities.