Operating systems and dynamic trust in a delocalized environment

The availability of Internet, the increase in the quality of service and the increase in the network output through the use of large bandwidth technology, even on the telephone lines, gives rise, for usual applications, to new modes of conception and run time settings for the usual public programs. In a usual setting the operating system checks authorizations associated with files at the beginning of a session and these are usually unchanged until the end of the session. In a delocalized environment the imported files that arrive through the network are not the property of the root. When a program is executed, important resident files can be and are modified by the imported program. This means that the root has to give control to an exterior entity, on a temporary and limited basis. This transfer of control has to be made in the setting of a trust policy that has to be determined beforehand. We propose a dynamic approach to trust. This passes through the fact that a new structure is needed for the manifest. It can be made of many lists, giving rise possibly to a tree of trust.