Nowadays many organizations share sensitive services through open network systems and this raises the need for an authorization framework that can interoperate even when the parties have no pre-existing relationships. Trust Negotiation is the process used to establish these first relationships, through the transfer of attributes, embedded in digital credentials, between the two parties. However, these attributes may themselves be considered sensitive and so may need protection from disclosure. In some environments, the policies that govern the protected services may also be considered sensitive and their release to arbitrary strangers may leak confidential business information. This paper describes a way to unify the protection of services, sensitive credentials and policies in a synchronized trustworthy manner. We propose a trust authorization framework (TAF) that builds on the capabilities of XACML to support the bilateral exchange of policies and credentials through trust negotiation.