With the rapid development of the Internet and the mobile value added services

the increasingly expansion of users and markets and the coming of Chinas 3G Time

the mobile value added services will be a bright spot to uplift the mobile communication industry. In this paper

the writer studied the security issue of transferring messages with mobile devices

and planned and realized the key management of OTA system by adding MAC (message authentication code) to ensure data security. It ensures the safety and completeness of the data transformation between the server and the USIM card; therefore it provides the guarantee to the launch of the mobile value added services.