Server-aided directly revocable ciphertext-policy attribute-based encryption with verifiable delegation

Abstract

Ciphertext-policy attribute-based encryption (CP-ABE) is a promising primitive for enforcing access control policies defined by data owner on outsourced data. We propose a novel primitive called server-aided directly revocable CP-ABE with verifiable delegation, denoted by sarCP-ABE. In sarCP-ABE, the workloads about revocation are delegated to an aide-server, and the data owner only needs to generate a normal ciphertext as in a pure CP-ABE system. A user can be directly revoked by updating a public revocation list. To prevent a revoked user from decrypting, the aide server can update the aide-ciphertext with current revocation list, and an auditor can publicly check the correctness of the updated aide-ciphertext. At last, the proposed scheme can be proved selectively secure against chosen-plaintext attack on both original and updated ciphertext.