Today, we have the ability to utilize scalable, distributed computing environment within the limits of the Internet, using a practice known as Cloud Computing. This phenomenon is generating a lot of interest worldwide because of its lower total cost of ownership, scalability, competitive differentiation, reduced complexity for customers, and faster and easier acquisition of services. While cloud offers several advantages, people come to the cloud computing topic from different points of view. The promise of providing interoperability in a heterogeneous world, as well as the possibility of offloading operations that require high processing power, make the mobile phones an ideal target device for accessing it. This increases the degree of exposure of critical resources which poses new challenges to securing data and service. This work presents how Cloud Computing can be accessed using a mobile phone, and how the communication between the Cloud Computing and the Mobile client can be secured. Targeted at analyzing the performance of impact on adding WS - Security a common security standard of SOAP-based web services.