An efficient cryptography mechanism should enforce an access control policy over the encrypted data to provide flexible, fine-grained, and secure data access control for secure sharing of data in cloud storage. To make a secure cloud data sharing solution, we propose a ciphertext-policy attribute-based proxy re-encryption scheme. In the proposed scheme, we design an efficient fine-grained revocation mechanism, which enables not only efficient attribute-level revocation but also efficient policy-level revocation to achieve backward secrecy and forward secrecy. Moreover, we use a multiauthority key attribute center in the key generation phase to overcome the single-point performance bottleneck problem and the key escrow problem. By formal security analysis, we illustrate that our proposed scheme achieves confidentiality, secure key distribution, multiple collusions resistance, and policy-or attribute-revocation security. By comprehensive performance and implementation analysis, we illustrate that our proposed scheme improves the practical efficiency of storage, computation cost, and communication cost compared to the other related schemes.
KEYWORDSattribute-level revocation, attribute-based access control, CP-ABE, policy-level revocation, public cloud storage
INTRODUCTIONCloud computing emerges as a new paradigm of computing that provides elasticity, scalability, and multitenancy on demand pay-per-use service model. 1 Specifically, cloud storage services enable a data owner to host data in the cloud, and enable a consumer to access the data through cloud server. 2 The adoption of a cloud storage service (eg, Dropbox, Google Drive, Microsoft and OneDrive) for storing, managing, and sharing the data has been gained significant attention in the real world. 3 However, privacy and security issues related to the user's data pose various challenges regarding data access control that impede the cloud storage system from wide adoption. 4-7 To prevent the unauthorized access of the sensitive data, a common method is to encrypt the data before uploading it to the cloud server. 8 The traditional public key encryption, 9 identity-based encryption (IBE), 10-12 and homomorphic encryption 13,14 cannot be directly used to impose the access control over the encrypted data in cloud environment. These methods ensure that the encrypted data can be decrypted by a single user, thus decreasing the flexibility and scalability of data access control in cloud environment.Int J Commun Syst. 2018;31:e3494.wileyonlinelibrary.com/journal/dac