随着多云模式的充分发展以及面向云计算数据多源的重要特点，传统基于单云单源数据模型的安全查询技术，由于缺乏多云协作分布式查询机制，难以处理大规模多源数据集，也无法保证多源数据的安全性。本项目研究多云多源模型下安全、灵活、高效的多云协作分布式安全查询技术，是在新模型下对云安全查询技术的新探索。首先，从查询和安全两个角度，对多云多源模型下的安全查询技术进行准确建模，构建系统模型和安全模型。其次，提出全面保护多源数据安全，且支持多云协作查询的高性能索引加密和查询令牌加密方案，实现多云协作富语义安全查询。再次，提出面向多源异构访问控制策略的安全索引和查询令牌授权加密方案，实现安全和灵活的多云协作授权查询。最后，面向不可信多云环境，提出查询结果被动和主动验证机制，利用验证、定位和跟踪技术抑制云服务器的非法行为，保证查询结果的正确性和完整性。本项目对促进云安全查询研究领域的新发展具有重要的理论意义。

Cloud computing is a representative Multi-Tenancy service mode, which provides services for numerous cloud users. Recently, multi-cloud collaboration, which is an important and promising application paradigm, has been fully developed. Traditional secure search technologies based on single cloud server provider single data source are difficult to handle with the large scale data set from multiple cloud users without the multi-cloud collaboration search mechanism. Moreover, it fails to fully ensure the security of data in the multi-source data environment. This project devotes to studying the secure, flexible, and efficient multi-cloud collaboration secure search technologies in the multi-cloud and multi-source data outsourcing setting, which is a new exploration of secure query technology in the new model. First, fully considering the data security and search feature in the multi-cloud multi-source model, the project will establish precise system and security models. Then, the novel encryption schemes of high-performance index and search token fully protecting multi-source data security will be proposed to achieve rich semantics secure searches in the multi-cloud cooperative manner. Next, the project will research the encryption of secure index and search token authorization orienting multi-source heterogeneous access control policy to achieve secure and flexible multi-cloud collaboration authorization search. Finally, considering untrusted multi-cloud threat model, the project will propose passive and active verification mechanisms to ensure the correctness and completeness of search results by using verification, location, and trace methods, which will be able to effectively restrain the dishonest behaviors of the cloud servers. This project has significant theoretical meaning in promoting the new development of secure search research field in cloud computing.