Securing the web services is an issue has always been with the development of the Internet. There are much more serious security issues in a web services due to its openness and autonomy.. Building a trust mechanism in web services environment is very important. This paper presented a trust model of choosing trusted source Web Services. Our system collects the trust evidence of the clients, defines the trust polices, builds up the trust levels of the clients based on the trust evidence and policies. As more evidence becomes available, the system iteratively updates the trust information including trust evidence and polices. This paper also focus on using evidence for making access control decisions in web services environments. Our approach views access control as the filtering of messages between communicating services. We implement our evidence-based approach with a mechanism analogous to a network firewall, filtering messages going to and from a service.

Keywords: Web Services, Access Control, Trust, Firewall, Evidence, Security.