Page 14 V- Access control Access control structures  Capacities: line representation  Use of tickets t=(o,P), where o is an object, and P a set of permissions: a subject holding t can access to o with permissions in P  A subject holding a capacity must not be able to modify it, or to build a new capacity  A subject may transfer the capacity to another subject  Used in micro-kernel L4, Capsicum, …  For a specific object it is difficult to know the set of subjects that can access to it  Requires mechanisms to revoke capacities o2 r,w,es2 o3 ws3 o3 r,es1 o1 r,w
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