A New Key Assignment Scheme for Enforcing Complicated Access Control Policies in Hierarchy

[[abstract]]In a traditional key assignment scheme, an access control policy is used to solve the access control problem in a hierarchy. A higher security class can access lower security classes, but the opposite is not allowed. However, in some cases, this can be troublesome because of the lack of flexibility. In this paper, we shall propose a secure key assignment scheme which can be performed not only in a hierarchy but also in more complicated policies with anti-symmetrical and transitive exceptions