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Contributory Broadcast Encryption with Efficient Encryption and Short Cipher texts

ABSTRACT:-

            Traditional broadcast encryption (BE) schemes allow sender to securely broadcast to any subset of members but require a trusted party to distribute decryption keys. Group key agreement (GKA) protocols enable a group of members to negotiate a common encryption key via open networks so that only the group members can decrypt the cipher texts encrypted under the shared encryption key, but a sender cannot exclude any particular member from decrypting the cipher texts. In this paper, we bridge these two notions with a hybrid primitive referred to as contributory broadcast encryption (ConBE). In this new primitive, a group of members negotiate a common public encryption key while each member holds a decryption key. A sender seeing the public group encryption key can limit the decryption to a subset of members of his choice. Following this model, we propose a ConBE scheme with short cipher texts. The scheme is proven to be fully collusion-resistant under the decision n-Bilinear Diffie-Hellman Exponentiation (BDHE) assumption in the standard model. Of independent interest, we present a new BE scheme that is aggregately. The aggregatability property is shown to be useful to construct advanced protocols.

EXISTING SYSTEM	PROPOSED SYSTEM
EXISTING CONCEPT:- BE schemes are also referred to as key distribution scheme sin some scenarios. In the public-key BE setting, the trusted center also generates public key for all the users so that anyone can play the role of a broadcaster or sender.	PROPOSED CONCEPT: - We present the Contributory Broadcast Encryption (ConBE) primitive, which is a hybrid of GKA and BE. Using the public encryption key, anyone can encrypt any message to any subset of the group members and only the intended receivers can decrypt.
EXISTING TECHNIQUE:- Broadcast Encryption(BE).	PROPOSED TECHNIQUE:- Contributory Broadcast Encryption (ConBE).
TECHNIQUE DEFINITION:- Broadcast encryption (BE) is a well-studied primitive intended for secure group-oriented communications. It allows a sender to securely broadcast to any subset of the group members. BE schemes which have (n1=2) complexity in the same performance metrics.	TECHNIQUE DEFINITION:- ConBE allows the sender to exclude some members from reading the cipher texts. We formalize collusion resistance by defining an attacker who can fully control all the members outside the intended receivers but cannot extract useful information from the cipher text.
DRAWBACKS:- Existing GKA protocols cannot handle sender/member changes efficiently. BE schemes in the literature are not aggregatable.	ADVANTAGES:- ConBE does not need a fully trusted third party to set up the system. Asymmetric GKA allow the sender to unilaterally exclude any particular member from reading the plaintext.