Conditional Identity-Based Broadcast Proxy Re-Encryption With Anonymity and Revocation

In recent years, many extended identity-based broadcast proxy re-encryption (IBPRE) schemes have been put forward. These schemes are flexible enough and feasible to various application scenarios, including conditional IBPRE, revocable IBPRE, and anonymous IBPRE. However, the existing extended IBPRE schemes are not able to simultaneously achieve fine-grained data sharing, identity privacy protection for authorized data users (DUs) and access privilege revocation. To this end, we put forward conditional identity-based broadcast proxy re-encryption with anonymity and revocation (CIBPRE-AR) and construct a concrete CIBPRE-AR scheme. The scheme implements fine-grained data sharing by associating conditions with the re-encryption key. The identity privacy protection for authorized DUs is provided by using Lagrange interpolation. Further, the access privileges of the violated DU are revoked by updating the re-encryption key. The indistinguishability of ciphertexts against chosen-plaintext attack and anonymity of the DUs are proved rigidly. Compared with existing similar schemes, only the CIBPRE-AR scheme simultaneously achieves fine-grained data access control, anonymity as well as revocation. The proposed scheme also has advantage with respect to computation cost.