Objective Model Architecture Mechanism What ? How ? Assurance

Information systems of the future will be large-scale, highly decentralized, pervasive, span organizational boundaries and evolve rapidly. EEective security in this cyberspace will require engineering authority and trust relationships across organizations and individuals. In this paper we propose the four-layer OM-AM framework for this purpose. OM-AM comprises objective , model, architecture and mechanism layers in this sequence. The objective and model (OM) layers articulate what the security objectives and tradeoos are, while the architecture and mechanism (AM) layers address how to meet these requirements. The hyphen in OM-AM emphasizes the shift from what to how. These layers are roughly analogous to a network protocol stack with a many-to-many relationship between successive layers, and most certainly do not imply a top-down waterfall-style software engineering process. OM-AM is an excellent match to the policy-neutral and exi-ble nature of role-based access control (RBAC). This paper describes and motivates the OM-AM framework and presents a case study in applying it in a distributed RBAC application.