In this paper, we investigate how an illegitimate user can use a reconfigurable intelligent surface (RIS) to maximally degrade the secrecy performance of the legitimate system. We first consider the case when the illegitimate user performs eavesdropping only. A problem is formulated to minimize the system secrecy rate by optimizing the phase shifts of the RIS elements. We also consider the case when the illegitimate user works with full-duplex technology and can perform eavesdropping and jamming simultaneously through the RIS. A problem is formulated to minimize the system secrecy rate by optimizing the jamming power and the phase shifts of the RIS elements. Although the two formulated problems are nonconvex, they are optimally solved in this paper. Our results show that good eavesdropping performance can be achieved by placing the RIS at an appropriate position. Further, jamming plus eavesdropping can largely reduce the secrecy rate of the legitimate system.

翻译：在本文中，我们研究了非法用户如何使用可重构智能表面（RIS）来最大限度地降低合法系统的保密性能。我们首先考虑只进行窃听的情况。我们提出了一个问题来通过优化RIS元件的相移来最小化系统保密率。我们还考虑了非法用户使用全双工技术并通过RIS同时进行窃听和干扰的情况。我们提出了一个问题来通过优化干扰功率和RIS元件的相移来最小化系统保密率。虽然这两个问题都是非凸的，但我们在本文中进行了最优解。我们的结果表明，通过将RIS放置在适当的位置，可以实现良好的窃听性能。此外，干扰加窃听可以大大降低合法系统的保密速率。