科研之友
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摘要
Broadcast encryption allows a data sender to encrypt data to a group of specified users via a public channel. Only those authorized users can decrypt the ciphertext. Unauthorized users learn nothing about the encrypted data even they collude. Broadcast encryption has been widely used in real-world applications for multi-user data sharing or secret sharing due to its merits, such as cloud computing and Internet of things. While the SM9 identity-based encryption algorithm designed by China is a Chinese encryption standard for protecting data privacy. Nevertheless, SM9 encryption algorithm is designed for the scenarios where the receiver is one only. In this paper, we fuse SM9 identity-based encryption algorithm and broadcast encryption, and propose the first identity-based broadcast encryption (IBBE) scheme based on SM9 under pairings. The construction idea is derived from Delerablée's IBBE scheme (Asiacrypt 2007). The proposed scheme features constant-size ciphertexts and private keys, which is independent of the number of receivers. More precisely, the ciphertext consists of three elements and user private key has one group element only. Compared to SM9 identity-based encryption algorithm, the ciphertext contains one additional group element. We give the definition of IBBE and corresponding security models, and formally analyze the security of the proposed scheme. The proposed scheme has been proved to be IND-sID-CPA secure in the random oracle model under a q-type GDDHE assumption. The theoretical analysis and demonstration show that the proposed scheme is comparable to the existing optimal IBBE schemes in terms of computational overheads and communication overheads.
