Abstract:

ZHANG Xuejun et al presented a multioriented traitor tracing scheme with fully collusion resistance. They asserted that it was computationally infeasible for any number of users to get a different key by collusion. Here, this scheme was cryptographically analyzed. We found that it does not meet the collusion resistance. Also, we proposed a concrete attack in which the three or more traitors can build more than one valid decrypt key unidentified by black box tracing method. MA Hua et al also proposed a traitor tracing scheme that can trace all traitors undoubtedly. However, we presented a simple attack in which traitors can easily avoid tracing by changing their keys.

Key words: traitor tracing；collusion resistance；RSA；collusion attack；broadcast encryption