In this paper, we shall formulate and address a problem of covert actuator attacker synthesis for cyber-physical systems that are modeled by discrete-event systems. We assume the actuator attacker partially observes the execution of the closed-loop system and is able to modify each control command issued by the supervisor on a specified attackable subset of controllable events. We provide straightforward but in general exponential-time reductions, due to the use of subset construction procedure, from the covert actuator attacker synthesis problems to the Ramadge-Wonham supervisor synthesis problems. It then follows that it is possible to use the many techniques and tools already developed for solving the supervisor synthesis problem to solve the covert actuator attacker synthesis problem for free. In particular, we show that, if the attacker cannot attack unobservable events to the supervisor, then the reductions can be carried out in polynomial time. We also provide a brief discussion on some other conditions under which the exponential blowup in state size can be avoided. Finally, we show how the reduction based synthesis procedure can be extended for the synthesis of successful covert actuator attackers that also eavesdrop the control commands issued by the supervisor.

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免费合成隐蔽执行器攻击者

在本文中，我们将制定并解决由离散事件系统建模的网络物理系统的隐蔽执行器攻击者综合问题。我们假设执行器攻击者部分观察了闭环系统的执行，并且能够修改监管者针对特定的可控事件子集发出的每个控制命令。由于使用了子集构造程序，我们提供了直接但通常指数级的时间减少，从隐蔽执行器攻击者合成问题到 Ramadge-Wonham 监督者合成问题。然后，可以使用已经开发的许多技术和工具来解决监督者综合问题来免费解决隐蔽执行器攻击者综合问题。特别地，我们表明，如果攻击者无法向监督者攻击不可观察的事件，则可以在多项式时间内进行减少。我们还简要讨论了可以避免状态大小指数膨胀的其他一些条件。最后，我们展示了如何将基于缩减的合成过程扩展到成功的隐蔽执行器攻击者的合成，这些攻击者也窃听了监督者发出的控制命令。