The “smart city” will provide numerous services via broadcasted encrypted data, such as a pin or key for paid users to access water service. These researchers go beyond data security and consider data access control and identity privacy for both active and revoked users. For example, a user may not want others to know that she has access to sensitive information or has subscribed to a particular group. The paper expands what the authors presented in 2016 at the Australasian Conference on Information Security and Privacy. It clearly has broad applications and is noteworthy.

They address the issue of “how to revoke some receivers after the ciphertext has been generated, but without revealing the message content and the identity information of receivers.” To solve this problem, according to the authors, they “propose a novel revocable identity-based broadcast encryption, which is suitable for better data access control and receiver identity information protection.”

In a logical sequence, the paper presents related work, preliminary definitions, security models, the symmetric bilinear map that they utilize, the construction of their scheme, and security analysis, with a brief discussion at the end of each section. Much of the paper is mathematical and some advanced knowledge of mathematics is required to understand it. There is a list of references and contact information for the five authors. I commend their research.