Co operative Query Answer Authentication Scheme.The data owner (DO) publishes the sensing data through the cloud server in the cloud service over crowd sensing data, so that the user can get interesting information on demand. But there are often untrustworthy cloud service providers (CSP).Concerns about privacy and security arise about the authenticity of the queryresponse and the DO identity leakage. Many researchers are studying the query response authentication scheme for the cloud service system to solve these problems.

The traditional technique is providing DO’s signature for the published data.But the signature would always reveal DO’s identity. Based on the ring signature, the Merkle hash tree (MHT) and the non-repudiable service protocol, this paper proposes a cooperative query response authentication scheme to address this disadvantage.The proposed scheme could not only verify the query response, but also protect the identity of the DO through cooperation between the entities in the cloud service system.First, it collects to sign MHT’s internal nodes, as well as the root node. Thus, in the best case, the complexity of the verification computation could be reduced significantly from O(log2N) to O(log2N0.5).

Then,to sign the selected nodes,it enhances an existing ring signature.In addition,the proposed scheme uses the non-repudiation protocol to protect trading behavior between the CSP and users during the transmission of query answer and verification object.The analysis of safety and performance demonstrates the safety and feasibiliy of the proposed scheme.Extensive experimental results show its superiority in the efficiency of verification and overhead communication.