|Ph.D Student||Somekh Baruch Anelia|
|Subject||Information Theoretic Analysis of Watermarking Systems|
|Department||Department of Electrical Engineering||Supervisor||Professor Neri Merhav|
In this work, watermarking systems are analyzed as a game between two players: an information hider, and a decoder, on the one hand, and an attacker on the other hand. The information hider is allowed to cause some tolerable level of distortion to the original data (covertext) within which the message is hidden, and the resulting distorted data can suffer some additional amount of distortion caused by an attacker who aims at erasing the message. It is assumed that the host data is drawn from a finite-alphabet memoryless stationary source. Two versions of the game are investigated: the private game where the covertext (side information) is available at the encoder and the decoder and the public game where it is available at the decoder only. Another problem that we consider is the problem of private fingerprinting in the presence of collusive attacks, which is modelled as a game between a fingerprinter and a decoder, on the one hand, and a coalition of two or more attackers, on the other hand. Motivated by a worst-case approach, we assume that the attacker is informed of the hiding strategy taken by the information hider and the decoder, while they are uninformed of the attacking scheme. This approach leads to the maximin error exponent and maximin coding capacity as objective functions. Single letter expressions for the coding capacities of the private and public watermarking games and the private fingerprinting game are found under some mild assumptions. A single-letter expression for the maximin private error exponent is found, and the asymptotically optimal strategies of the players in the various games are characterized as well.