hello shaima ,, 

I think you must create your basic idea and then you can use the cloud computing services to reduce the load/overhead of your basic work and by the load I mean the (storage ,energy, security ...etc.).

Hi  Shaimaa Abdelnabi .....

SDN + NFV approach to  have more flexible and secure  IoT with TinySDN combined to WSN-ETESec and key agreement protocol. 

Best Regards....

I hope you can go through the site such as :-

http://zapthink.com/2012/04/18/cloud-oriented-architecture-and-the-internet-of-things/

https://www.cetic.be/IMG/pdf/120606-GDD-IoT-SICS.pdf

http://personal.ee.surrey.ac.uk/Personal/P.Barnaghi/doc/PID2759565-PDFexpressPLUS.pdf

This will surely help you

I want to make something concern cloud of sensor security