Identity-Based Broadcast Encryption Schemes for Open Networks

A Broadcast Encryption (BE) scheme allows a sender to safely transmit messages to a dynamically chosen set of system users via insecure channels. An identity-based encryption scheme is a public key encryption scheme that can take arbitrary strings as public keys. This paper presents an identity-based broadcast encryption scheme (IBBE) for open networks where senders, including the entities outside the system, have the ability to broadcast messages to any subset of the system users but only the target receivers can retrieve the messages. Compared with a recently introduced primitive referred to as contributory broadcast encryption (CBE), our scheme has comparable properties and is more practicable: the cost of our scheme is much lower and the total number of the system users can be efficiently changed.