טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentOrna Sumszyk
SubjectInformation Embedding with Reversible Stegotext and Related
Problems
DepartmentDepartment of Electrical Engineering
Supervisor Full Professor Steinberg Yossef
Full Thesis textFull thesis text - English Version


Abstract

Information embedding (IE) or watermarking is the transmission of a message embedded into a host signal, in a way that is invisible to the unintended observer. This problem has received considerable attention in recent years, due to its wide range of applications, e.g., copyright protection systems, source tracing and covert communications. The signal resulting of the embedding process is called the composite signal, or the stegotext. It is transmitted through a channel to the destination that decodes the message. However, the user at the destination may be interested in retrieving the host signal too. The quality of restoration of the host data can even be of utmost importance in some applications such as medical imagery and military communications. Reversible information embedding (RIE) extends the IE model by adding the requirement of decoding the host signal. In some applications however, this requirement is too strong and a high price has to be paid in the rate of communication. For example, if the user is interested in decoding the message and further transmitting it to another destination embedded into the same host, it suffices to reproduce the stegotext at the destination. This work expands the study of IE channels by adding the requirement of retrieving the stegotext at the destination. This new model is called the Stegotext Reversible Information Embedding (SRIE). A single-letter characterization of the achievable rate-distortion region is developed. In particular, it is shown that a rate higher than the RIE capacity can be achieved, under the (more relaxed) requirement of stegotext decoding. The duality of this problem to  the Common Reconstruction model developed by Steinberg is discussed. Two binary examples are solved, and an iterative algorithm that computes numerically the capacity is provided. Then, an extension to the Multiple Access Channel for the SRIE model is provided where two independent data streams are embedded into dependent host signals. Inner and outer bounds on the capacity region are developed. Finally, an extension of this model to the Broadcast Channel is provided and a single-letter characterization of the capacity region is derived.