Implementing a passive network covert timing channel

The paper concerns passive network covert timing channels, in which the channel senders reside in intermediate nodes (e.g. router, gateway) and forward the passing-by packets in a carefully planned manner to covertly transmit the information. In this study, we focus on constructing and testing a kind of passive network covert timing channel, in which the information is hidden in the transmission interval between two adjacent packets. We first introduce three channel states to cope with the fluctuation in the traffic used as carrier, and explore how to select suitable values for the channel parameters to obtain high communication performance. We then implement an actual channel using Video On Demand (VOD) traffic as carrier, and obtain the communication characteristics of the channel. Finally, we investigate an information transmission scheme over the channel, including frame design, frame synchronization and error correction.