Fighting Pirates 2.0

In this paper we propose methods to cope with the Pirates 2.0 attack strategy against tracing and revoking schemes presented at Eurocrypt 2009. In the Pirates 2.0 attack model traitors collaborate in public and partially share their secret information with a certified guarantee of anonymity. Several classes of tracing and revoking schemes are subject to such a new threat. We focus our attention on the tree-based class of schemes. We start by discussing some simple techniques which can partially help to deal with the attack, and point out their limits. Then, we describe a new hybrid scheme which can be used to face up the Pirates 2.0 attack strategy.