An improvement of discrete Tardos fingerprinting codes
It has been known that the code lengths of Tardos's collusion-secure fingerprinting codes are of theoretically minimal order with respect to the number of adversarial users (pirates). However, the code lengths can be further reduced, as some preceding studies on Tardos's codes already revealed. In this article we improve a recent discrete variant of Tardos's codes, and give a security proof of our codes under an assumption weaker than the original assumption (Marking Assumption). Our analysis shows that our codes have significantly shorter lengths than Tardos's codes. For example, in a practical setting, the code lengths of our codes are about 3.01%, 4.28%, and 4.81% of Tardos's codes if the numbers of pirates are 2, 4, and 6, respectively.