History and Evolution of Steganography
Steganographic techniques have been used for ages and they date back to ancient Greece. The aim of steganographic communication back then and now, in modern applications, is the same: to hide secret data (a steganogram) in an innocently looking cover and send it to the proper recipient who is aware of the information hiding procedure. In an ideal situation the existence of hidden communication cannot be detected by third parties.
What distinguishes historical steganographic methods from the modern ones is, in fact, only the form of the cover (carrier) for secret data. Historical methods relied on physical steganography – the employed media were: human skin, game, etc.. Further advances in hiding communication based on the use of more complex covers, e.g. with the aid of ordinary objects, whose orientation was assigned meaning. This is how semagrams were introduced. The popularisation of the written word and the increasing literacy among people had brought about methods which utilised text as carrier. The World Wars had accelerated the development of steganography by introducing a new carrier – the electromagnetic waves. Presently, the most popular carriers include digital images, audio and video files and communication protocols. The latter may apply to network protocols as well as any other communication protocol (e.g. cryptographic).
The way that people communicate evolved over ages and so did steganographic methods. At the same time, the general principles remained unchanged.
For detailed review of historical steganographic methods see the Links section or read our paper on hidden data carrier evolution:
E. Zielinska, W. Mazurczyk, K. Szczypiorski, The Advent of Steganography in Computing Environments - In: Computing Research Repository (CoRR), abs/1202.5289, arXiv.org E-print Archive, Cornell University, Ithaca, NY (USA), published on 23 February 2012 [.pdf]
Recent advances and modern usage of steganography are presented below: