Cloud computing is emerging as a prevalent data interactive paradigm to realise user's data remotely stored in an online cloud server. Cloud services provide great conveniences for the users to enjoy the on-demand cloud applications without considering the local infrastructure limitations. During the data accessing, different users may be in a collaborative relationship, and thus data sharing becomes significant to achieve productive benefits. But security and privacy issues are becoming key concerns in data sharing among the multiple users in cloud storage. In order to avoid all these things, a system is proposed in which a shared authority based privacy-preserving authentication protocol to solve privacy and security issue for cloud storage.