In this letter, we provide a physical layer supported defense mechanism against traffic analysis attacks by exploring the covert communication capability of digital modulation schemes. We analyze and compare the performances of M-PSK, M-QAM, M-ASK and M-APSK modulations in terms of the probability of detection by a warden and the maximum achievable throughput at the receiver. We obtain a lower bound for the covert transmission probability at Willie, which can be utilized as a covertness limit to maximize the throughput. Numerical studies highlight the tightness of the presented lower bound and show the maximum achievable throughput limits without being detected by a traffic analysis attacker.

中文翻译：

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流量分析攻击的对策：采用数字调制的秘密通信

在这封信中，我们通过探索数字调制方案的隐蔽通信能力，提供了一种物理层支持的防御机制，可抵御流量分析攻击。我们根据看守的检测概率和接收器可达到的最大吞吐量来分析和比较M-PSK，M-QAM，M-ASK和M-APSK调制的性能。我们在Willie处获得了秘密传输概率的下限，可以将其用作秘密限制以最大化吞吐量。数值研究突出显示了所提出的下限的紧密性，并显示了可被流量分析攻击者检测到的最大可实现吞吐量限制。