关键词: 属性基加密, 密文策略, 访问策略, 授权

Abstract: In most attribute-based encryption schemes, access policy, which is used to encrypt message by encryptor, is often sent to the decryptor along with the ciphertext, but sometimes the policy itself is sensitive. This paper proposed a new construction to hide the access policy. During the encryption process, encryptor achieve the indistinguishability between the well-formed ciphertext components and the malformed. Compared with other constructions, ours was more efficient by reducing the times of exponent and pairing, and the sizes of ciphertext and keys were smaller. In addition, new attributes could be added in the ciphertext policy after setup was executed and the existing public parameters can remain unchanged. These analyses show the flexibility of construction. Security gets proved based on decisional bilinear Diffie-Hellman assumption.

Key words: Attribute-Based Encryption （ABE）, ciphertext policy, access policy, authoriztion