Abstract: Cloud computing has evolved as the current major technology in IT industry .Among many services provided by the cloud, data service has much importance and is very much susceptible as the data can be shared and modified by different users in the group . As the cloud cannot be trusted, the owner of the data can delegate the task of checking integrity of the shared data .In this paper a study is made on some proxy re-signature schemes and also a public auditing scheme using the idea of proxy re-signatures for efficient integrity checking of data

Keywords: Integrity, Proxy, cloud, shared data