Public cloud architecture offers a public access software service. Users can login to access the cloud resources via various devices. The main advantage of the SaaS (Software as a Service) cloud service is that it supports different software and devices, in order to open web browsers, to authenticate the users through the standard format. E-books are protected by digital rights management (DRM), and users can use mobile devices to read them. However, the users' identity need to be authenticated or the communication between the user and the cloud server will be at risk. The processes by which users submit their proof of identity to the cloud needs to be protected. In this paper, information security can be achieved efficiently via cloud server architecture and a cryptography mechanism. The proposed scheme focuses on using a mobile device to access the cloud service. The DRM mechanisms can protect digital content; once the mobile users pass the authentication they can access the cloud services, with authenticated users able to easily use mobile devices to read digital content.