Efficient attribute-based data sharing in mobile clouds

Ciphertext-policy attribute-based encryption (CP-ABE) is extremely suitable for cloud computing environment in that it enables data owners to make and enforce access policies themselves. However, most of existing CP-ABE schemes suffer severe efficiency drawbacks due to large ciphertext size and computation cost, and hence are not suitable for mobile clouds, where users are usually resource-limited. In this paper, we first present a generic attribute-based data sharing system based on a hybrid mechanism of CP-ABE and a symmetric encryption scheme. Then, we propose a CP-ABE scheme which features constant computation cost and constant-size ciphertexts. The proposed CP-ABE scheme is proven selective-secure in the random oracle model under the decision n-BDHE assumption, where n represents the total number of attributes in universe. It can efficiently support AND-gate access policies with multiple attribute values and wildcards. Theoretical analysis and experimental results indicate that the proposed scheme is extremely suitable for data sharing in mobile clouds. (C) 2015 Elsevier B.V. All rights reserved.