Trust Management Languages and Complexity

Trust management is a concept of automatic verification of access rights against distributed security policies. A policy is described by a set of credentials that define membership of roles and delegation of authority over a resource between the members of roles. Making an access control decision is equivalent to resolving a credential chain between the requester and the role, which members are authorized to use a resource. A credential is an electronic document, formulated using a trust management language. This way, trust management languages are a tool for describing credentials and specifying access control policies in a flexible and modifiable way. This paper discusses the expressive power of trust management languages, describes a new extension to Role-based Trust Managements language RT, and evaluates the complexity of algorithm that is used for answering security queries.