Privacy preserving integrity checking of shared dynamic cloud data with user revocation

In Cloud computing, storage and maintenance of the data are provided as service to the client. Traditionally, when the clients store and maintain their data at their own server, the data are dynamic in nature and are often shared among groups of users. The clients desire the traditional flexibility when they shift their data to the Cloud. Introducing the flexibility of sharing dynamic data with storage outsourced to the Cloud needs addressing new security challenges and requires the provision for user revocation. This paper presents a secure and effective scheme for storage of shared dynamic data in untrusted cloud servers with provisions for privacy preserving integrity check by third-party auditor and for addition and revocation of users. This proposed scheme is based on CDH-based ring signature and vector commitment.