Access right management by extended password capabilities

With reference to a classic protection system featuring active subjects that reference protected objects, we approach the problem of identifying the objects that each subject can access, and the operations that the subject can carry out on these objects. Password capabilities are a classical solution to this problem. We propose a new form of password capability, called extended password capability (or e-capability, for short). An e-capability can specify any combination of access rights. A subject that holds a given e-capability can generate new e-capabilities for reduced sets of access rights. Furthermore, a subject that created a given object is in a position to revoke the access permissions granted by every e-capability referencing this object, completely or in part. The size of an e-capability is comparable to that of a traditional password capability. The number of passwords that need to be stored in memory permanently is kept to a minimum, and is equal to a single password for each object