A Revocable Outsourced Data Accessing Control Scheme with Black-Box Traceability

Ciphertext-policy attribute-based encryption (CP-ABE) is a promising solution to the fine-grained access control problem of encrypted data. Several CP-ABE-based cryptographic cloud storage systems have been proposed in recent years. However, existing CP-ABE schemes still have several limitations that make them not effective to be used in a practical application. Firstly, decryption privileges may be changed when the user revocation happens to prevent the leakage of encrypted data. Secondly, malicious users may delegate decryption keys to unauthorized users for profit. Thirdly, the complex operation of encryption and decryption may bring a huge computational cost and is usually considered to be a heavy burden for system users. Therefore, this paper proposes a new CP-ABE scheme ROBBT-CPABE, which can provide attribute revocation, black-box tracking, outsourcing encryption, and outsourcing decryption. By using the information distribution algorithm and the secure modular exponentiation outsourcing algorithm, the scheme can achieve attribute revocation and outsource some expensive encryption and decryption operations to the cloud server. Based on the construction of indistinguishable traceable ciphertext, the proposed scheme can support black-box tracking. Then the ROBBT-CPABE scheme is formally proved to be selective replay chosen ciphertext attack (RCCA) secure and black-box traceable secure. Performance analysis demonstrates the efficiency and practicality of ROBBT-CPABE.