Outsource the Ciphertext Decryption of Inner Product Predicate Encryption Scheme Based on Prime Order Bilinear Map

In the private index predicate encryption scheme, the ciphertext not only hides the message, but also hides the attributes. Predicate encryption scheme can enforce the fine grained access control over the encrypted data and perform selective search on the encrypted data. However, the main efficiency drawback of predicate encryption scheme is that the size of the ciphertext and the time required to decrypt it scale with the complexity of the predicate. In this work, we proposed a novel inner product predicate encryption scheme with verifiable outsourced ciphertext decryption based on prime order bilinear group, which significantly reduces the overhead of the data consumer. In the proposed scheme, the data consumer provides the cloud server with a transformation key with which the cloud server transforms the ciphertext associated with the attributes which satisfy the predicate associated with the private key into a simple and short ciphertext, and thus it significantly reduces the time for the data consumer to decrypt the ciphertext, whereas the cloud server does not know the underlying plaintext message for any data consumer; simultaneously, the data consumer can check whether the transformation done by the cloud server is correct to verify the correctness of the transformation.