New bounds for frameproof codes

Frameproof codes are used to fingerprint digital data. They can prevent copyrighted materials from unauthorized use. In this paper, we study upper and lower bounds for w-frameproof codes of length N over an alphabet of size q. The upper bound is based on a combinatorial approach and the lower bound is based on a probabilistic construction. Both bounds can improve one of the previous results when q is small compared with w , say cq≤ w for some constant c ≤ q. Furthermore, we pay special attention to binary frameproof codes. We show a binary w-frameproof code of length N cannot have more than N codewords if N < (w+1/2).