An Efficient Revocable Attribute-Based Signcryption Scheme with Outsourced Designcryption in Cloud Computing

Sensitive data sharing through cloud storage environments has brought varies and flexible secure demands. Attribute-based signcryption (ABSC) is suitable for cloud storage because it provides combined data confidentiality and authentication, and fine-grained data access control. While, the existed ABSC schemes hardly support efficient attribute revocation. In addition, the heavy computational overhead of ABSC limits the applying resource-constrained device in cloud storage environments. In this paper, to tackle the above problems, we propose an efficiently revocable attribute-based signcryption scheme with decryption outsourcing. The proposed scheme achieves the efficient attribute revocation through delegating the cloud server to update ciphertext without decrypting it. During the decryption phase, it outsource massive decryption operations to the proxy server so that computation cost on user's devices is small and constant. The security analysis proves the correctness, confidentiality, collusion resistance, unforgeability and forward secrecy of our scheme. Furthermore, performance analysis shows that our scheme is efficient in terms of the ciphertext, key size and computation cost while realizing desired functions.