A new traitor tracing

A traitor tracing scheme is a broadcast encryption scheme in which a provider can trace malicious authorized users who illegally gave their personal keys to unauthorized users. The conventional schemes have some problems one of them is that there exists an upper bound on the sizes of keys to certify the security of the scheme against a collusion attack by many traitors, and so that the size of the header increases according to the increase of the bound. We shall propose a new traitor tracing scheme where the header size is independent of the number of traitors.