Physical-layer authentication (PLA) mechanisms exploit signals exchanged at the physical layer of communication systems to confirm the sender of a received message. In this paper, we propose a novel challenge-response PLA (CR-PLA) mechanism for a cellular system that leverages the reconfigurability property of a reconfigurable intelligent surface (RIS) (under the control of the verifier) in an authentication mechanism. In CR-PLA, the verifier base station (BS) sets a random RIS configuration, which remains secret to the intruder, and then checks that the resulting estimated channel is modified correspondingly. In fact, for a message sent by an attacker in a different location than the legitimate user equipment (UE), the BS will estimate a different channel and the message will be rejected as fake. Such a solution reduces the communication and computational overhead with respect to higher-layer cryptographic authentication. We derive the maximum a-posteriori attack when the attacker observes a correlated channel and the reconfigurable intelligent surface (RIS) has many elements, and the attacker transmits to Bob either directly or through the RIS. Using a generalized likelihood ratio test to test the authenticity at the base station (BS), we derive approximate expressions of the false alarm and misdetection probabilities when both the BS and the UE have a single antenna each, while the RIS has a large number of elements. We also evaluate the trade-off between security and communication performance, since choosing a random RIS configuration reduces the data rate. Moreover, we investigate the impact of various parameters (e.g., the RIS randomness, the number of RIS elements, and the operating signal-to-noise ratio) on security and communication performance.

中文翻译：

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使用可重构智能表面的质询-响应身份验证分析


物理层身份验证 （PLA） 机制利用在通信系统的物理层交换的信号来确认接收消息的发送者。在本文中，我们提出了一种用于蜂窝系统的新型质询-响应 PLA （CR-PLA） 机制，该机制在身份验证机制中利用了可重构智能表面 （RIS） 的可重构性（在验证者的控制下）。在 CR-PLA 中，验证器基站 （BS） 设置随机 RIS 配置，该配置对入侵者保持机密，然后检查生成的估计信道是否相应地被修改。事实上，对于攻击者在与合法用户设备 （UE） 不同的位置发送的消息，BS 将估计不同的通道，并且该消息将作为假消息被拒绝。这种解决方案减少了与更高层加密身份验证相关的通信和计算开销。当攻击者观察到一个相关信道并且可重构智能表面 （RIS） 具有许多元素，并且攻击者直接或通过 RIS 传输给 Bob 时，我们得出了最大的 a-posteriori 攻击。使用广义似然比检验来检验基站 （BS） 的真实性，当 BS 和 UE 各有一个天线，而 RIS 具有大量元件时，我们得出了误报和误检概率的近似表达式。我们还评估了安全性和通信性能之间的权衡，因为选择随机 RIS 配置会降低数据速率。此外，我们还研究了各种参数（例如 RIS 随机性、RIS 元素的数量和工作信噪比）对安全性和通信性能的影响。