In cloud computing, a network of computers handles all the heavy lifting work of running the applications that your computers have to do. In the last decade cloud storage has also become popular. Users are outsourcing their data on cloud, losing the physical possession of the data. By doing this the users have considerably eased their responsibility and costs of onsite data storage and expensive maintenance but have embarked on a yet another challenge of checking the integrity of data in cloud. Cloud storage involves usage of remotely located large data centers for storing user data on which the user actually does not have any control. This has introduced the requirement of facilitating public auditability for cloud storage, so that the users can rely on Third Party Auditor for checking the integrity of data stored in cloud. But the TPA should not introduce new threats to user's data privacy and should not increase online burden on cloud user. This paper proposes a secure cloud storage scheme which supports privacy preserving public auditing. We have proposed the use of public key based homomorphic authenticator with random masking.