Describe the scheme of capability lists to implement protection?
Capability lists (C- lists):
These lists are utilized to make sure that uses only access files that are explicitly authorized access. These files contain
(i) files created by a user herself/himself
(ii) files owned by others, for that a user process explicit access privileged granted through other owners.
C-list: A capability is a file access privilege relating capabilities possessed through a user is stored in a capability list. A C-list is a set of pairs{ (file.id, access privileges),.....}
C-lists are generally small in size. It limits the space and time over heads in utilizing them to control file accesses. A c-list is a token representing specific access privileges for an object. An object is any software or hardware entity in the system. A capability possessed through a process. A process possessing, it is a capability for an object can access the object in a way reliable with the access privileges explained in the capability. Therefore maintaining C-lists give:
1. A uniform addressing mechanism for short and long life objects
2. This does not explicitly associate memory along with processes. This associates C-lists along with processes.
3. A process may access objects existing anywhere into the system.