The advent of Cryptographically Relevant Quantum Computers (CRQCs) presents a fundamental and existential threat to the forensic integrity and operational safety of Industrial Control Systems (ICS) and Operational Technology (OT) in critical infrastructure. This paper introduces a novel, forensics-first framework for achieving quantum resilience in high-consequence environments, with a specific focus on nuclear power plants. We systematically analyze the quantum threat landscape across the Purdue architecture (L0-L5), detailing how Harvest-Now, Decrypt-Later (HNDL) campaigns, enabled by algorithms like Shor's, can retroactively compromise cryptographic foundations, undermine evidence admissibility, and facilitate sophisticated sabotage. Through two detailed case studies, \textsc{Quantum~Scar} and \textsc{Quantum~Dawn}, we demonstrate multi-phase attack methodologies where state-level adversaries exploit cryptographic monoculture and extended OT lifecycles to degrade safety systems while creating unsolvable forensic paradoxes. Our probabilistic risk modeling reveals alarming success probabilities (up to 78\% for targeted facilities under current defenses), underscoring the criticality of immediate action. In response, we propose and validate a phased, defense-in-depth migration path to Post-Quantum Cryptography (PQC), integrating hybrid key exchange, cryptographic diversity, secure time synchronization, and side-channel resistant implementations aligned with ISA/IEC 62443 and NIST standards. The paper concludes that without urgent adoption of quantum-resilient controls, the integrity of both physical safety systems and digital forensic evidence remains at severe and irreversible risk.

翻译：密码学相关量子计算机（CRQCs）的出现，对关键基础设施中工业控制系统（ICS）与运营技术（OT）的取证完整性和运行安全构成了根本性且关乎存续的威胁。本文提出了一种新颖的、取证优先的框架，旨在实现高后果环境（特别是核电站）的量子韧性。我们系统分析了普渡架构（L0-L5）各层面临的量子威胁态势，详细阐述了由Shor等算法实现的“现在收集，稍后解密”（HNDL）攻击活动，如何能够追溯性地破坏密码学基础、削弱证据可采性，并促成复杂的蓄意破坏。通过\textsc{Quantum~Scar}和\textsc{Quantum~Dawn}两个详细案例研究，我们展示了国家级对手利用密码学单一性和OT系统长生命周期，分阶段实施攻击的方法论，这些攻击旨在削弱安全系统，同时制造无法解决的取证悖论。我们的概率风险模型揭示了令人担忧的成功概率（在当前防御措施下，针对特定设施的成功率高达78\%），凸显了立即采取行动的紧迫性。作为应对，我们提出并验证了一个分阶段、纵深防御的向后量子密码学（PQC）迁移路径，该路径集成了混合密钥交换、密码学多样性、安全时间同步以及抗侧信道攻击的实现方案，并与ISA/IEC 62443和NIST标准保持一致。本文的结论是，若不紧急采用具备量子韧性的控制措施，物理安全系统和数字取证证据的完整性都将面临严重且不可逆转的风险。