Dynamic frameproof codes

There are many schemes in the literature for protecting digital data from piracy by the use of digital fingerprinting, such as frameproof codes, which prevent traitorous users from colluding to frame an innocent user, and traitortracing schemes, which enable the identification of users involved in piracy. The concept of traitor tracing has been applied to a digital broadcast setting in the form of dynamic traitor-tracing schemes and sequential traitor-tracing schemes, which could be used to combat piracy of pay-TV broadcasts, for example. In this thesis we explore the possibility of extending the properties of frameproof codes to this dynamic model. We investigate the construction of l-sequential c-frameproof codes, which prevent framing without requiring information obtained from a pirate broadcast. We show that they are closely related to the ordinary frameproof codes, which enables us to construct examples of these schemes and to establish bounds on the number of users they support. We then define l-dynamic c-frameproof codes that can prevent framing more efficiently than the sequential codes through the use of the pirate broadcast information. We give constructions for schemes supporting an optimal number of users in the cases where the number c of users colluding in piracy satisfies c ≥ 2 or c = 1. Finally we consider sliding-window l-dynamic frameproof codes that provide ongoing protection against framing by making use of the pirate broadcast. We provide constructions of such schemes and establish bounds on the number of users they support. In the case of a binary alphabet we use geometric structures to describe constructions, and provide new bounds. We then go on to provide two families of constructions based on particular parameters, and we show that some of these constructions are optimal for the given parameters.