Broadcast encryption is a scheme which only allows qualified users to decrypt published content. Typically users are separated into subscribed users who have access to the content and unsubscribed users who do not have the access. Conventional broadcast encryption scheme uses a master secret key to encrypt the content which results in only a trusted designer of the system is allowed to produce encrypted content. This type of broadcast encryption is commonly used in Conditional Access System (CAS) such as Cable-TV.
More recently another type of broadcast encryption scheme called public key broadcast encryption was proposed which consists of a system-wide public key. With this public key, every user can produce encrypted content which only a subset of users can decrypt with their own private keys.