Constant-size cryptographic evidence records are increasingly used to build audit trails for regulated AI workloads in clinical, pharmaceutical, and financial settings, where each execution is summarized by a compact, verifiable record of code identity, model version, data digests, and platform measurements. Existing instantiations, however, typically rely on classical signature schemes whose long-term security is threatened by quantum-capable adversaries. In this paper we formalize security notions for evidence structures in the presence of quantum adversaries and study post-quantum (PQ) instantiations and migration strategies for deployed audit logs. We recall an abstraction of constant-size evidence structures and introduce game-based definitions of Q-Audit Integrity, Q-Non-Equivocation, and Q-Binding, capturing the inability of a quantum adversary to forge, equivocate, or rebind evidence items. We then analyze a hash-and-sign instantiation in the quantum random-oracle model (QROM), assuming an existentially unforgeable PQ signature scheme against quantum adversaries, and show that the resulting evidence structure satisfies these notions under standard assumptions. Building on this, we present three migration patterns for existing evidence logs: hybrid signatures, re-signing of legacy evidence, and Merkle-root anchoring, and analyze their security, storage, and computational trade-offs. A case study based on an industrial constant-size evidence platform for regulated AI at Codebat Technologies Inc. suggests that quantum-safe audit trails are achievable with moderate overhead and that systematic migration can significantly extend the evidentiary lifetime of existing deployments.

翻译：恒定大小的密码学证据记录正日益用于构建临床、制药和金融场景中受监管AI工作负载的审计追踪，其中每次执行均通过一个紧凑且可验证的记录进行概括，该记录包含代码身份、模型版本、数据摘要和平台度量。然而，现有实现通常依赖于经典签名方案，其长期安全性受到具备量子计算能力的对手的威胁。本文形式化了量子对手存在下证据结构的安全概念，并研究了已部署审计日志的后量子（PQ）实现与迁移策略。我们回顾了恒定大小证据结构的抽象模型，并引入了基于博弈定义的Q-审计完整性、Q-非抵赖性和Q-绑定性，以刻画量子对手伪造、抵赖或重新绑定证据项的能力缺失。随后，我们在量子随机预言机模型（QROM）中分析了一种哈希-签名实现，假设存在一种针对量子对手的、存在性不可伪造的PQ签名方案，并证明在标准假设下，所得证据结构满足上述安全概念。在此基础上，我们提出了三种现有证据日志的迁移模式：混合签名、遗留证据的重新签名以及Merkle根锚定，并分析了它们的安全性、存储和计算权衡。基于Codebat Technologies Inc.用于受监管AI的工业级恒定大小证据平台的案例研究表明，量子安全的审计追踪可通过适度开销实现，且系统化迁移可显著延长现有部署的证据生命周期。