Public auditing for shared data in cloud with safe user revocation

Cloud computing is a most adopted emerging technology by all organizations. Data storage and sharing of data in cloud is the most used services, whereas secure public auditing makes challenge in such services. Since cloud infrastructure which is not a trustable, users in the group for data sharing must compute their signatures and shares their block for integrity auditing. Any corruption, insider attack of data is possible in an outsourced data from users to cloud. All Participants in the sharing group can also able to modify data along with the access. If any user does any malicious activities, Group manager can revoke such user from group so revoked user cannot be part of sharing. The major challenges of data security is integrity of outsourced data in cloud is analyzed and proposes a privacy preserving public auditing mechanism where Third Party Auditor is used for integrity checking of data and Proxy resignature mechanism is used for re-signing keys for revoked users from the group. Additionally to avoid collusion between cloud and revoked user, our system uses secret sharing scheme called Cheater identifiable sharing based on Shamir's sharing scheme. The scheme identifies the dishonest user in the group which helps for efficient user revocation by group manager.