Steganography is a general term referring to all methods for the embedding of additional secret content into some form of carrier, with the aim of concealment of the introduced alterations. The choice of the carrier is nearly unlimited, it may be an ancient piece of parchment, as well as a network protocol header. Inspired by biological phenomena, adopted by man in the ancient times, it has been developed over the ages. Present day steganographic methods are far more sophisticated than their ancient predecessors, but the main principles have remained unchanged. They typically rely on the utilization of digital media files or network protocols as a carrier, in which secret data is embedded. This paper presents the evolution of the hidden data carrier from the ancient times till the present day and pinpoints the observed development trends, with special emphasis on network steganography.

This work addresses the issues related to network steganography in IEEE 802.15.4 Wireless Personal Area Networks (WPAN). The proposed communication scheme employs illicit Direct Sequence Spread Spectrum code sequences for the transmission of steganographic data. The presented approach is a compromise between minimising the probability of covert channel disclosure and providing robustness against random errors and a high steganographic data rate. The conducted analyses show that it is possible to create a covert channel with a data rate comparable to the raw data rate of IEEE 802.15.4 without much impact on the perceived receiver sensitivity, the Chip Error Rate and the Bit Error Rate.