Web Services Trust Language (WS-Trust) is a specification that uses the secure messaging mechanisms of WS-Security to facilitate trust relationships in diverse Web service environments. WS-Trust is an integral part of the Microsoft model for a standards-based distributed identity infrastructure. WS-Trust also an important element of Windows CardSpace, an interface intended for the exchange of user identity information in Microsoft .Net 3.0.
WS-Trust defines a request/response process for the exchange of security tokens in Kerberos, X.509 and SAML (Security Assertion Markup Language). The intent is to ensure operability for the exchange of security information between different technologies, operating systems or domains. WS-Trust allows multiple security tokens to be combined, supporting identification of a service in conjunction with a separate security token for each individual subscriber. WS-Trust can supplement existing security technologies and methods.