A Novel Post-Quantum Approach: "Proof-Of-Decay" (Cryptographic Half-Life) for Unmigrated Dormant UTXOs

Relying on a decay-based mechanism to address quantum security in cryptocurrency systems presents several critical flaws. The fundamental issue lies in its inability to remove the incentives for quantum attackers. Instead of deterring malicious actors, it transforms the process into an optimization challenge. Attackers with rational strategies would simply wait until the grace period concludes and then execute coordinated, large-scale sweeps to extract value from exposed UTXOs, rendering the decay ineffective as a deterrent.

Another significant weakness is the assumption that quantum advancements will proceed at a predictable, linear pace over multiple years. This overlooks the possibility of sudden breakthroughs in algorithms or hardware that could accelerate the timeline for breaking cryptographic keys. In such circumstances, adversaries could exploit vulnerabilities and drain legacy UTXOs before the decay function has a chance to substantially reduce their balances. Consequently, this model fails to safeguard funds against rapid, unpredictable progress in quantum computing.

Finally, implementing time-based reductions in wallet balances imposes penalties on passive holders without addressing the underlying vulnerability. If a legacy wallet is already compromised, this approach harms legitimate owners by diminishing their assets over time, while simultaneously enabling attackers to optimize their extraction strategy for maximum gain. Thus, the decay model not only fails to solve the core problem but also introduces new disadvantages for genuine users.