Abstract: A large number of data are generated by the public city departments and citizen in modern city, and modern information and communication technology and network technology are adopted to use and process the massive data. To protect the privacy and data security of users, the encryption algorithm is used to encrypt the data in the process of data transmission. Broadcast encryption is the most effective method in multi-user environment. Traditionally, the ciphertext of identity-based broadcast encryption can be broadcasted to a group of receivers, and the identity of the receiver is contained in the ciphertext. When multiple receivers decrypt the ciphertext, the identity information of other users will be exposed. In order to protect the identity privacy between receivers, an identity-based privacy-preserving broadcast encryption algorithm  is proposed, which realizes the anonymity between receivers. In addition, the algorithm   focuses how to revoke some re-ceivers of the specified target from the ciphertext of anonymous broadcast and determines the user's data access authority according to the data access control policy, so as to provide users with the revocation of ciphertext. The revocation process does not reveal the plaintext and the identity information of the receivers. In the random oracle model, the security of the algorithm   is proved based on the BDH difficulty problem, and the effectiveness and security of the algorithm   are verified by the simulation experiment on the actual data set.

Key words: smart city, identity-based encryption, broadcast encryption, revocation, privacy-preserving