This paper addresses fault diagnosis and tampering detection in discrete event systems modeled with nondeterministic finite automata under malicious attacks. We propose a novel structure to simultaneously track the occurrence of fault events and tampering actions in systems compromised by attacks (i.e., by arbitrary deletions, insertions, or substitutions of observed symbols). Assuming that each deletion, insertion, or substitution bears a positive cost to the attacker, two scenarios are taken into account: (1) a bounded number of attacks or, more generally, a total cost constraint on tampering actions, and (2) an unbounded number of attacks or, more generally, no constraints on the total cost of tampering actions. Several examples are presented to demonstrate the influence of cost constraints on tamper-tolerant diagnosis and tampering detection. A state isolation technique is developed to deal with the fault and/or tampering action detection problem via an external observer that aims to isolate the estimated states within a certain subset of states based on a given sequence of observations. We also report a technique of polynomial complexity for verifying tamper-tolerant diagnosability and tampering detectability.

中文翻译：

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成本约束下离散事件系统中的容错性诊断分析和篡改检测


本文讨论了在恶意攻击下使用非确定性有限自动机建模的离散事件系统中的故障诊断和篡改检测。我们提出了一种新的结构，可以同时跟踪受攻击（即任意删除、插入或替换观察到的符号）的系统中故障事件和篡改操作的发生。假设每次删除、插入或替换都会给攻击者带来正成本，则考虑了两种情况：（1） 有限数量的攻击，或者更一般地说，对篡改操作的总成本限制，以及 （2） 无限数量的攻击，或者更一般地说，对篡改操作的总成本没有限制。本文提供了几个示例来说明成本约束对防篡改诊断和篡改检测的影响。开发了一种状态隔离技术，通过外部观察器处理故障和/或篡改操作检测问题，旨在根据给定的观察序列隔离特定状态子集内的估计状态。我们还报道了一种多项式复杂性技术，用于验证防篡改诊断性和篡改可检测性。