移动云计算是移动网络和云计算的一种融合，它为移动用户提供最优化的服务。除了云计算的基础安全问题以外，移动云计算的主要安全问题在终端一方，即移动用户安全。移动用户安全具有一些特殊的和密码学相关的问题，例如移动设备的资源受限问题，移动用户的身份信息保护问题，以及移动用户的数字版权管理问题等。 本项目致力于研究云计算访问控制常用算法-属性基加密/签名算法-的服务器辅助计算方案，将解密/验证计算任务安全分配，由云服务器执行较重的计算任务，将轻量级计算任务交给移动设备，以此来应对移动设备的资源受限问题；另外，致力于研究可聚合代理重签密，应对基于半可信第三方的个人身份信息保护问题，使得移动用户请求某项云服务时，根据云服务的需求，仅提交部分身份信息进行认证；我们还将致力于研究无需配对的身份基代理重加密，应对基于半可信第三方的移动用户数字版权管理问题，使得只有已付费的合法用户才能获得数字产品的解密密钥。

Mobile cloud computing is a combination between mobile network and cloud computing, and it provides optimal services for mobile users. Except for the basic security problems in cloud computing, the main security problems in mobile cloud computing exist in the mobile user. The security of mobile user has some special security problems related to cryptography, for example, the resource limitation for mobile devices, protection of mobile user's privacy identity information, and digital right management of mobile users etc. The project research the server-aided decryption/verification protocols for attribute based encryption/verification schemes, which are related to access controlling in cloud computing, to resolve the problem of limited resource in mobile devices. In the server-aided decryption/verification protocols, the computational task is securely divided, and the heavy one is assigned to the cloud server while the light one is assigned to source constrained devices. Furthermore, we research the aggregate proxy re-signcryption scheme to solve the problem that how to protect the mobile users's personal identity information with the semi-trusted third party. When the mobile user applies for a cloud service, it only provide a small part of his indentity information according to the request of cloud service for authentication. We also research the identity based proxy re-encryption without pairing to resolve the problem of digital rights management for mobile users based on the semi-trusted third party. Only if the valid mobile user has paid for a digital product, he can receive the correct decryption key.