Anonymous Attribute-Based Encryption with Large Universe and Threshold Access Structures

Although ciphertext-policy attribute-based encryption (CP-ABE) is promising for realizing fine-grained attribute-based data sharing, attribute privacy protection issues remain to be solved. In this paper, we propose an anonymous CP-ABE scheme (ANON-CP-ABE) and prove its security under the Decisional Modified Bilinear Diffie-Hellman assumption. In the proposed scheme, the sensitive attribute values are not sent along with the ciphertext and hence users' attribute privacy is preserved. Our ANON-CP-ABE scheme allows threshold access structures and the decryption test only involves attribute name indexes. In particular, the proposed ANON-CP-ABE scheme supports large attribute universe and the public parameter size is small and constant.