International Association for Cryptologic Research (IACR)
Abstract
Several appealing features of cloud computing such as cost-effectiveness and user-friendliness have made many users and enterprises interested to outsource their sensitive data for sharing via cloud. However, it causes many new challenges toward data confidentiality, access control , scalability, and flexibility. Ciphertext-policy Hierarchical attribute-based encryption (CP-HABE) can be a promising solution to the mentioned problems. But, the existing HABE schemes have several limitations in their key delegation and user revocation mechanisms.
In this work, to solve these problems, we introduce the concept of \textit{fully distributed revocable } CP-HABE (FDR-CP-HABE) system and propose the first FDR-CP-HABE scheme. The proposed scheme provides a high level of flexibility and scalability in the key delegation and user revocation mechanisms. Moreover, our proposed system is pairing-free and realizes lightweight computing in decryption phase. Indeed,
by exploiting the computational operation outsourcing technique, most of the operations have been done by the powerful cloud service provider and very few computations have been leaved to the data user. Also, in our scheme the storage cost on the data user side has been decreased, compared to the other similar works. Moreover, using the hardness assumption of Decisional Bilinear Diffie-Hellman (DBDH) problem, we show that the proposed scheme is adaptively semantically secure in the standard model
