Cloud Computing is a technology where users can remotely store their data into the cloud environment so as to have the on-demand applications and services from the common pool of computing resources. By this, users can be relieved from the burden of local data storage and maintenance. However maintaining data integrity over Cloud environment is a very challenging task. Our proposed public auditability technique for cloud data security is of significant importance so that users can route to an external audit party to check the data integrity of outsourced data when it is needed. In this paper we make use of the public key based homomorphic authenticator with random mask method to achieve the privacy public auditability for data storage security in cloud and also with the fair share algorithm we are maintaining fair network bandwidth allocation. Our proposed public auditability and fair share technique achieves high security, performance, and also provide less communication and computation overhead.