中文摘要：

着各种私有云或公有云的普及应用，云计算的安全问题成了热点。在其他学者对于云计算安全研究的基础上，探讨了目前自由云计算环境下的主要安全风险，构建一个基于第三方可信云的安全协调工作方案，并对其结构和原理进行了具体的分析。第三方可信云包括身份认证、密钥发布和数据传输、监控管理三个主要模块，该方案有利于各种云实体安全协同工作且可行性高。

英文摘要：

With a variety of private cloud or public cloud universal applications, security issues of cloud computing have become a hot spot. On the basis of other scholars research of cloud security, this paper discusses major security risks in free cloud computing environments nowadays, constructs a secure collaborative work scheme on the basis of the third party credible cloud, and analyzes its detailed structure and principles. The third credible cloud includes three main modules： authentication, key distribution and data transmission, and monitoring management. The scheme conduces to a variety of cloud entities security and is of high feasibility.