Abstract
Cloud computing is the concept of using the large amount of remote services through a network using various least amount of resources, it provides these resources to users via internet. These storage systems provide a large virtual storage. When people relocate from web applications to cloud computing platform. There are many critical problems appeared with cloud computing such as security, privacy and reliability etc. But we find that security is the most important between these problems. The traditional form of accessing cloud services is to use a username and password as a security token. During login time, new security theft may arise like account/password sniffing, virtualization attack, or phishing attack.