Ph.D Student | Somekh Baruch Anelia |
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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.