A Probabilistic Framework for Forecasting Cryptographic Security Under Quantum and Classical Threats

This paper presents a probabilistic, multi-layered framework designed to forecast the longevity and security of cryptographic systems under the dual pressures of classical and quantum computational threats. The model integrates thermodynamic decay analogies, stochastic transitions via Hidden Markov Models, and an adapted financial option pricing method to quantify cryptographic degradation, strategic risk, and transition readiness. This framework can guide standardization roadmaps, cipher retirement, or quantum-migration planning, guiding proactive, instead of reactive, crypto agility. Furthermore, it provides a quantitative methodology to complement the current opinions expressed in surveys, as well as a qualitative approach to cryptographic security risk projections.