ABSTRACT
Ciphertext-Policy Attribute-Based Encryption (CP-ABE) is especially suitable for access control system in cloud computing environment. In most of the existing CP-ABE schemes, the length of the ciphertexts increases linearly with the complexity of the access policy, so that the expenses are very expensive. To tackle the challenge above, we propose an attribute-based encryption scheme for constant-length ciphertexts in this paper. The algorithm limits the length of the ciphertext and the computation of the bilinear pairing in fixed value, improving the efficiency of the system. Apart from this, it introduces hierarchical authorizations to reduce the burden and risk of the single authorization. As a result, it achieves a high efficiency, fine and scalable access control. The scheme supports the situation which has a plurality of attribute values and wild-card AND strategy. Furthermore, the scheme is proved secure under the assumption of (t, ε, l) – BDHE.
