Fundamental Limits of Activity-Based Covert Channels
Fundamental Limits of Activity-Based Covert Channels
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DOI：
10.1109/globecom46510.2021.9686016
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发表时间：
2021-12
期刊：
影响因子：
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通讯作者：
Ke Li;Majid Ghaderi;D. Goeckel
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作者：
Ke Li;Majid Ghaderi;D. Goeckel
隐蔽通信考虑发送者Alice与预期接收者Bob可靠地通信而不被对手管理员Willie检测到的能力。隐蔽信号的一种方法是爱丽丝改变系统的状态，使改变后的状态向鲍勃传递信息。最近的工作的基础上的隐蔽通信，在很大程度上考虑了物理层的动机，我们提供了一个基本特征的一种方法，通过活动隐蔽信令：采用预共享的码本与鲍勃，爱丽丝编码的消息，从码本中选择适当的模式的插槽插入无害的数据包到时隙ALOHA系统中存在的其他用户。预期接收者Bob检测时隙ALOHA系统的活动中的模式以确定发送了哪个码字。我们提供了一个基本的分析，这样一个系统的性能下的隐蔽性约束。首先，我们考虑的信令方案时，鲍勃或威利有各种能力来辨别在一个给定的时隙中的数据包的数量，特别是为拟议的信道。考虑到这种设计中的挑战，我们接下来认识到，来自光通信的技术虽然被设计用于不同的信道，但可以潜在地被采用，从而产生提供可实现速率的下限的一大类方案。数值结果提供支持的分析发展，并通过这种方法来展示潜在的隐蔽信号。
Covert communication considers the ability of transmitter Alice to communicate reliably to intended receiver Bob without being detected by adversary warden Willie. One collection of approaches to covert signaling is for Alice to alter the state of a system in such a way that the altered state conveys information to Bob. Motivated by recent work on the foundations of covert communications that has largely considered the physical layer, we provide a fundamental characterization of one approach to covert signaling via activity: employing a codebook pre-shared with Bob, Alice encodes a message by selecting from the codebook the appropriate pattern of slots to insert innocuous packets into a slotted ALOHA system in the presence of other users. The intended recipient Bob detects patterns in the activity of the slotted ALOHA system to determine which codeword was sent. We provide a fundamental analysis of the performance of such a system under a covertness constraint. First, we consider signaling schemes derived specifically for the proposed channel when Bob or Willie has various abilities to discern the number of packets in a given slot. Given the challenges in such design, we next recognize that techniques from optical communications, although designed for a different channel, can potentially be employed and thus yield a large class of schemes that provide lower bounds on the achievable rate. Numerical results are provided to support the analytical development and to demonstrate the potential of covert signaling through such an approach.