Application developers require cloud solutions that offer a highly scalable and secure development environment. Some Platform-as-a-Service (PaaS) solutions fail to meet the security requirements of developers, administrators, and final users in a satisfactory and flexible manner. While some providers do offer secure cloud solutions, users are obliged to redesign and adapt their applications in order to conform to the provided environment. The present work introduces MagosCloud Secure, a highly-scalable, opportunistic, declarative, and secure solution constructed on the basis of MagosCloud[1], designed to meet the needs of traditional and e-science application developers. It allows the deployment of a variety of platforms, providing an access control model whereby developers may declaratively state how they wish their data and application resources to be automatically shared with other users. It relies on the concept of ‘separation of concerns’, such that developers need only be concerned with creating their applications, entrusting MagosCloud Secure with the responsibility of providing a secure, highly scalable platform. Finally, the results of tests concerning the automatic generation of secure platforms, as well as run time considerations, are analyzed.