Physical layer secret key generation is a promising candidate to achieve one-time-pad encryption approach for the wireless communication system. However, in a static environment, the secret key rate is low due to the lack of channel time-variation. To solve this problem, this letter proposes a novel secret key generation scheme assisted by an intelligent reflecting surface with discrete phase shifts. In the scheme, legitimate nodes construct the dynamic time-varying channel by rapidly and randomly switching the phase of IRS elements. Then, channel coefficients are used to generate the secret key. Based on the IRS channel model, we derive the probability distribution of the channel coefficient and the expressions of the secret key rate. Furthermore, we optimize the secret key rate by adjusting the switching time of the IRS phase. Monte Carlo simulation and numerical results show that our proposed scheme can update the secret key in a static environment.

中文翻译：

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静态环境中离散相移的智能反射表面辅助密钥生成


物理层密钥生成是实现无线通信系统一次性一密加密方法的有希望的候选者。然而，在静态环境中，由于缺乏信道时变性，密钥率较低。为了解决这个问题，本文提出了一种由离散相移智能反射面辅助的新型密钥生成方案。该方案中，合法节点通过快速、随机地切换IRS元素的相位来构建动态时变信道。然后，使用信道系数来生成密钥。基于IRS信道模型，推导了信道系数的概率分布和密钥率的表达式。此外，我们通过调整IRS阶段的切换时间来优化密钥率。蒙特卡洛模拟和数值结果表明，我们提出的方案可以在静态环境中更新密钥。