Biblio

To achieve a fine-grained access control function and guarantee the data confidentiality in the cloud storage environment, ciphertext policy attribute-based encryption (CP-ABE) has been widely implemented. However, due to the high computation and communication overhead, the nature of CP-ABE mechanism makes it difficult to be adopted in resource constrained terminals. Furthermore, the way of realizing varying levels of undo operations remains a problem. To this end, the access matrix that satisfies linear secret sharing scheme (LSSS) was optimized with Cauchy matrix, and then a user-level revocation scheme based on Chinese Remainder Theorem was proposed. Additionally, the attribute level revocation scheme which is based on the method of key encrypt key (KEK) and can help to reduce the storage overhead has also been improved.