Improving privacy-preserving CP-ABE with hidden access policy
User's privacy-preserving has become an urgent problem with the rapid development of cloud technologies. Anonymous ciphertext-policy Attribute Based Encryption (CP-ABE) not only protects the security of data, but also ensures that the privacy of the data user is not compromised. However, most of the known schemes have some shortcomings where those schemes either cannot achieve compact security or are inefficient in Encryption and Decryption. Additionally, recent works show the reality of the anonymity in some proposed schemes is doubtful. To address the problems above, we use the double exponent technique to construct an anonymous CP-ABE scheme which is more compact than the results at present. The proposed scheme with hidden access policy works in prime order groups. Meanwhile, we prove the security of our scheme under the decisional n-BDHE and decisional linear assumption.