Ciphertext Policy Attribute Based Encryption with Efficient Revocation

Revocation is a vital open problem in almost every cryptosystem dealing with malicious behaviors. In ciphertext policy attribute based encryption, unlike traditional public key cryptosystem, different users may hold the same functional secret keys related with the same attribute set leading to additional difficulties in designing revocation mechanism. In this paper, we propose the ciphertext policy attribute based encryption scheme with efficient revocation which can be proved secure in the standard model. Our construction uses linear secret sharing and binary tree techniques as the underlying tools. In addition to assigned attribute set, each user is also assigned with a unique identifier. Therefore, a user can be easily revoked by using his/her unique identifier; on the other hand, the encryption and decryption algorithms of ABE (Attribute Based Encryption) can be done without any involvement of these unique identifiers. Then, we prove the chosen plaintext security of our construction based on Decisional Bilinear Diffie-Hellman (DBDH) assumption in the standard model. Finally, we provide some discussion on the efficiency of our scheme and the extensions including delegation capability and chosen ciphertext security.