High Quality Content by WIKIPEDIA articles! Broadcast encryption is the cryptographic problem of encrypting broadcast content (e.g. TV programs) in such a way that only qualified users (e.g. subscribers who`ve paid their fees) can decrypt the content. The challenge arises from the requirement that unsubscription of some users should not affect the remaining users. The problem is further complicated by the fact that there is typically more than one data stream ("channel"), each of which may have a different set of subscribers. Several solutions exist offering various tradeoffs between the increase in the size of the broadcast, the number of keys that each user needs to store, and the feasibility of an unqualified user or a collusion of unqualified users being able to decrypt the content.