An Adaptively Secure Identity-Based Broadcast Encryption using CAST Algorithm

An adaptively secure identity-based broadcast encryption system featuring constant sized ciphertext is introduced. The size of public key and private keys of the system are both linear in the maximum number of receivers. The system is fully collusion-resistant and has stateless receivers. Here, in the system CAST algorithm is used for encryption of the broadcast message. The scheme is well optimized for broadcast encryption. The computational complexity of decryption depends only on the number of receivers and not on the maximum number of receivers of the system. A dual system encryption technique is used and adaptive security under general subgroup decisional assumption is proposed.