A Group Based Identity Anonymity and Secure Cloud Storage Scheme

Cloud storage is becoming more and more popular as its various advantages. However the security problems especially identity protection and data security problems have prevent the further development of this technology. Recently, K.Govinda et al. proposed an identity anonymity and secure data storage scheme basing on group signature algorithm which has made some improvements in some aspects of the above problems. However we find that the group member's secret key is kept on the group manager's hands, this is a very dangerous thing, because if the group manager betrays the group or is suffered from network attacks, all the member's secret will lost in the criminals' hands. In addition, we also find that their scheme may be suffered from man-in-the-middle attack, data tampering attack and data replaying attack. What's more? Their protocol also lacks the data download portion, which is an indispensable part of cloud storage. So in this paper, we will introduce K.Govinda et al.'s scheme first, then we will analysis that their scheme will be suffered from lots of attacks and has some shortcomings. After that we will propose our improved scheme by modifying the group signature scheme which will let each member's private key keep secret, changing the vulnerability messages in original protocols, adding a SHA-1 digest to prevent data tampering by cloud provider and adding the missing part of data download phase. At last we will make a performance simulation to make a comparison of our scheme and the traditional scheme.