An ID-based group-oriented decryption scheme secure against adaptive chosen-ciphertext attacks

ID-based decryption allows a sender to encrypt a message to an identity without access to a public key certificate. This paper proposes an ID-based group-oriented decryption scheme, secure against adaptive chosen-ciphertext attacks, which allows the sender to determine an access structure and generate a valid ciphertext on the chosen message. The correctness of decryption shares can be checked to detect when dishonest users in the access structure provide fake decryption shares. As a result, the message can be cooperatively recovered by users in the determined access structure. The formal proof of security of our scheme is based on the bilinear Diffie-Hellman problem in the random oracle model. Our proposed scheme is more efficient and provides higher security confidence than those in Li et al.'s certificate-based group-oriented decryption scheme. (C) 2009 Elsevier B.V. All rights reserved.