We deal with the problem of a center sending a message to a group of users such that some subset  of the users is considered revoked and should not be able to obtain the content of the message. We  concentrate on the stateless receiver case, where the users do not (necessarily) update their state from  session to session. We present a framework called the Subset-Cover framework, which abstracts a variety  of revocation schemes including some previously known ones. We provide sufficient conditions that  guarantee the security of a revocation algorithm in this class. We describ