In this paper we unveil basic properties of a code Γq for digital fingerprinting based on a projective plane of order q. We consider a situation where a coalition of malicious users generates a pirated digital content in which a binary sequence w is embedded subject to the marking assumption. Here, the size of the coalition is assumed to be less than or equal to a known constant c ≥ 2. We evaluate the number of candidates of the coalition that can also generate w subject to the marking assumption. It is shown that the number of such candidates is completely determined as a function of w for the case of c = 2. In addition, we give a sufficient condition under which all the malicious users are correctly identified from w for the case of c ≥ 3. Relationships between Γq and other existing classes of codes are discussed as well.

In recent years, with the rapid growth of the Internet as well as the increasing demand for broadband services, live pay-television broadcasting via the Internet has become a promising business. To get this implemented, it is necessary to protect distributed contents from illegal copying and redistributing after they are accessed. Fingerprinting system is a useful tool for it. This paper shows that the anti-collusion code has advantages over other existing fingerprinting codes in terms of efficiency and effectivity for live pay-television broadcasting. Next, this paper presents how to achieve efficient and effective anti-collusion codes based on unital and affine plane, which are two known examples of balanced incomplete block design (BIBD). Meanwhile, performance evaluations of anti-collusion codes generated from unital and affine plane are conducted. Their practical explicit constructions are given last.