| Attribute-based encryption and broadcast encryption are two important multi-receiver public key cryptosystem which can provide information protection in network multimedia information services such as digital pay TV, teleconference and so on, has broad prospects and important research significance. The ciphertext of both cryptosystems contain some of the personal information of users, so that only the authorized users can decrypt the ciphertexts successfully, and sometimes these personal information may be confidential information. Therefore, to realize anonymous encryption scheme which is important for privacy protection has been a hot research direction.This paper mainly focuses on multi-receiver public key cryptography, analyzes the reason of non-anonymous cryptosystems, proposes two efficient anonymous schemes that can protect personal information, and studies the effects of anonymity on security and efficiency of the schemes with multi receivers. The detailed research results are as follows:1) Using asymmetric pairings, an anonymous ciphertext-policy attribute-based encryption scheme is proposed in prime order bilinear group in this paper. The scheme is proven fully secure under the standard model based on the asymmetric decisional bilinear Diffie-Hellman assumption. Moreover, it has constant size private key, ciphertext and number of pairing operations. The proposed scheme improves security and dfficiency when compared with the ones in groups of composite order.2) We also propose an outsider-anonymous identity-based broadcast encryption(IBBE) scheme and the unauthorized users cannot obtain the identities of authorized users. Compare to the previous anonymous IBBE schemes, the scheme has constant size ciphertext, decreases the computation load. And based on the asymmetric decisional bilinear Diffie-Hellman Exponent assumption, it is proven secure without random oracles. The proposed scheme improves efficiency and security of anonymous IBBE schemes simultaneously.For the two schemes, we also give detailed security proof and performance comparison with other related ones. |
