Increasingly, today's mobile devices provide users a high level of convenience and flexibility. But, mobile devices are vulnerable to theft and loss, greatly increasing the likelihood of exposing sensitive data. To address this problem, Corner and Noble gave the concept of transient authentication and built a wearable token system, called ZIA system. In this paper, we design a new wearable token system using the idea of transient authentication. Our system not only preserves the same security characteristics as ZIA system, but also is more effective than ZIA system. In our system, careful key management and prudent communication mechanism allow significant performance enhancements. Due to the power constraint of the wearable token and the wireless link, the lower the costs are, the greater the chance of success the wearable token system has in practical implementation.