An Improvement of Tardos's Collusion-Secure Fingerprinting Codes with Very Short Lengths

The code length of Tardos's collusion-secure fingerprinting code (STOC'03) is of theoretically minimal order with respect to the number of malicious users (pirates); however, the constant factor should be further reduced for practical implementation. In this paper we give a collusion-secure fingerprinting code by mixing recent two improvements of Tardos code and modifying their pirates tracing algorithms. Our code length is significantly shorter than Tardos code, especially in the case of fewer pirates. For example, the ratio of our length relative to Tardos code in some practical situation with 4 pirates is 4.33%; while the lowest among the preceding codes in this case (Skoric et al., 2007) is 9.87%.