This thesis examines the issues relating to non-discretionary access controls for decentralized computing systems. Decentralization changes the basic character of a computing system from a set of processes referencing a data base to a set of processes sending and receiving messages. Because messages must be acknowledged, operations that were read-only in a centralized system become read-write operations. As a result, the lattice model of non-discretionary access control, which mediates operations based on read versus read-write considerations, does not allow direct transfer of algorithms from centralized systems to decentralized systems. This thesis develops new mechanisms that comply with the lattice model and provide the necessary functions for effective decentralized computation. Secure