Covert Channels in Secure Wireless Networks

Covert channels are unexpected and hidden communication paths embedded within a communication system that violate the system security policy. Covert communication occurs when a user or application deliberately manipulates and embeds in formation into some property of a communication system in such a way that the embedded information is not apparent to the legitimate users of the communication system. Internet based covert channels with low bit rates are enough to convey critical information such as network encryption keys or system access codes. This paper discusses how the threat of covert channels can be applied to secure wireless networks through the design and implementation of a working covert communication system. The resulting communication system reliably communicates private information in the presence of noise. In this case noise is other legitimate network traffic using the same encrypted link. The covert channel implementation presented here has been tested on a live network with background noise traffic and demonstrates the feasibility and limitations of the design.