A Tracing Algorithm for Short 2-Secure Probabilistic Fingerprinting Codes Strongly Protecting Innocent Users

We give a tracing algorithm for 2-secure probabilis- tic fingerprinting codes with the property that it never accuses innocent users when there are up to 2 attackers. Moreover, by using our code and tracing algorithm, innocent users are also unlikely to be accused even if either the number of attackers or attackers' abilities exceed our assumption. Our code is the first example of collusion-secure fingerprinting codes with both of these two properties. Furthermore, our code has shorter length among the preceding 2-secure codes, and possesses further properties desirable in a practical use.