We say that an encryption scheme is group-oriented if the parties involved in encryption and decryption are more than two in number. To date, many group-oriented encryption applications have been addressed. In the following, we review well-known applications that have appeared in the literature.

Broadcast encryption: Consider the problem of broadcasting digital contents to a large set of authorized users. Such applications include paid-TV systems, copyrighted CD/DVD distributions, and fee-based online databases. The problem is that anyone connected to a broadcast channel is able to pick up the data, whether they are authorized or not. To prevent unauthorized users from extracting data, the broadcaster encrypts the message and only the authorized users have the decryption keys to recover the data. However, the proposed method carries out n encryptions for each copy of data, where n is the number of subscribers.
Traitor tracing. In broadcast encryption, malicious authorized users, called traitors, may use their personal decryption keys to create a pirate decoder. The resulting pirate decoder allows an unauthorized user to extract the context. To discourage authorized users from revealing their keys, traitor tracing is first introduced by Chor, et al. The idea is an algorithm that uses the confiscated pirate decoder to track down at least one colluder without wrongly accusing non colluders with high probability. Most of these traitor-tracing schemes use a secret-key encryption scheme to encrypt data. A public-key traitor tracing allows everyone to perform encryption, and thus anyone can broadcast messages to authorized users securely.
Threshold cryptosystems. Within a group, various access policies are possible. Depending on the internal organization of the group and the access type of the message imposed by the sender, a different cryptographic scheme with the corresponding key management policy is needed. Threshold cryptosystems allow one to send encrypted messages to a group, while only a group achieving a “threshold" has the ability to reconstruct the plaintext.