System and method for secret communication

Abstract

We present a communication system which enables two or more parties to secretly communicate through an existing digital channel which has a primary function other than this secret communication. A first party receives a series of cover data sets, hides a certain amount of auxiliary data in the cover data sets, and then relays these cover data sets containing hidden data to a second party, aware of the hidden data. This second party may then extract the hidden data and either restore it to its original state (the state it was in before the first party received it) and send it along to its original intended destination, or may just simply extract the hidden auxiliary data. There exist a plethora of techniques for hiding auxiliary data in cover data, and any of these can be used for the hiding phase of the system. For example, in a JPEG cover data set, a Huffman table may be modified in such a way as to have no impact on the observable nature of the image, and several such schemes are presented here. Since there are so many ways in which to exploit a particular cover data set for secret communication, it is necessary that the first and second parties have pre-established a set of rules by which they will communicate. There must be agreement on the hiding technique, cover data type and location of the hidden data within the cover.