Bitcoin Developers Propose a 'Wait and React' Strategy to Counter Quantum Computing Threats

The Bitcoin community is considering a novel approach to addressing the potential risks posed by quantum computing: instead of imposing a pre-emptive freeze on vulnerable coins, the network would wait for an attacker to demonstrate their capabilities and then react. This 'wait and react' strategy relies on a 'canary' system, which involves placing a small amount of bitcoin in a special address that can only be unlocked by a quantum-capable attacker. If the attacker claims the bounty, the network would automatically trigger a freeze on older wallets. This approach is designed to provide an alternative to the controversial BIP-361 proposal, which would impose a fixed five-year timeline for phasing out vulnerable addresses and invalidating old signature schemes. Critics of BIP-361 argue that it undermines Bitcoin's core principle of private key holder control and could result in the permanent freezing of unmigrated coins. The 'canary' system, on the other hand, introduces a financial incentive for attackers to come forward, allowing users to contribute to a bounty that rewards the first entity to demonstrate a quantum attack. Additionally, the system includes a 'safety window' that makes stealth attacks more difficult by restricting the movement of vulnerable coins for an extended period. However, this approach rests on the assumption that the first entity capable of breaking Bitcoin would prefer to claim the bounty rather than executing a large-scale theft, which may not be a reliable bet. If this bet fails, Bitcoin may face the worst of both worlds: the catastrophic consequences of a quantum attack and the realization that a fixed-timeline defense could have prevented it.