Abstract: With the development of cloud computing,identity management issues of cloud computing have attracted great attention．Being widely used in cloud identity management,the identity authentication mechanism based on group signature guarantees that the cloud service provider cannot backtrack users’ identity information through outsourcing data,but it cannot prevent a malicious user from accessing cloud services．To solve the problem,the paper designed an identity management model by integrating trust management with group signature mechanism．The model calculates the user’s trustworthiness firstly,and then divides the users into groups according to the trustworthiness．At last,using the group signature mechanism,our model implements the authentication,which not only ensures user privacy in cloud but also helps the cloud providers to protect cloud services．Experiments show that the model can identify the malicious users effectively,and help the cloud service providers to prevent a malicious user from getting access to cloud services.

Key words: Trust management,Group signature,Identity management,Cloud computing