Because of their ability to enable new forms of cryptanalysis, quantum computers pose a threat to the cryptographic algorithms that are widely used to secure contemporary computer systems. A practical quantum computer may emerge within the next ten years or so, but due to theorised "harvest now, decrypt later" style attacker behaviour, mitigations are necessary today. Recent advances in cryptography and security architecture show promise in supporting the design of systems that exhibit resilience against quantum-enabled cryptanalysis, however there is a key gap in the literature around the subject of deriving tolerances for such systems. In this paper, we introduce the concept of rotation time as a measure of crypto agility, and derive an approximation that links rotation time tolerance to security risk tolerance. Historical CVE data is used to calculate illustrative values for rotation time tolerance, which is found to be of the order of hours to days. This demonstrates that using crypto agility in conjunction with hybrid encryption is an effective approach for designing quantum-resilient systems, but may necessitate challenging technical and operational tolerances in order to meet organisational risk tolerances.

翻译：由于量子计算机能够实现新的密码分析形式，它们对广泛用于保护当代计算机系统的密码算法构成了威胁。实用量子计算机可能在未来十年左右出现，但由于理论上存在的“先收集、后解密”式攻击者行为，现今就必须采取缓解措施。密码学与安全架构的最新进展在支持设计具备抗量子密码分析能力的系统方面展现出前景，然而，关于此类系统容限推导的文献中仍存在一个关键空白。本文引入了轮转时间概念作为密码敏捷性的一种度量，并推导出一个将轮转时间容限与安全风险容限联系起来的近似关系。利用历史CVE数据计算出的轮转时间容限示例值显示，其量级在数小时至数天之间。这表明，将密码敏捷性与混合加密相结合是设计抗量子系统的一种有效方法，但为了满足组织风险容限，可能需要在技术和运维层面设定具有挑战性的容限。