Fully Secure Traceable and Revocable-Storage Attribute-Based Encryption with Short Update Keys via Subset Difference Method

In order to achieve access control in cloud storage, we consider making use of attribute-based encryption (AUE) which has many excellent properties and can achieve fine-grained access control. Revocable-storage AUE (RS-AUE) is an extension of revocable ABE (R-ABE) which supports not only the revocation functionality but also the ciphertext update functionality. But nearly all known RS-AUE schemes used the complete subtree (CS) method for key revocation which would result in long update keys. In this paper, we construct a comprehensive traceable and revocable-storage AUE (TRS-ABE) scheme with the properties of traceability and revocation simultaneously with full security. In addition, we propose a novel technique to use the subset difference (SD) method instead of the CS method for our TRS- AUE scheme to efficiently reduce the size of update keys based on the recent work of Lee, Choi, Lee, Park, and Yung (Asiacrypt 2013) who firstly introduced a new cryptographic primitive called self-updatable encryption (SUE) which realized a time-updating mechanism. At last, we give its overview proof of full security in the standard model under three static assumptions.