Protection structures in computer systems

Protection against accidental or maliciuos destruction of information is an important feature in computer systems. A related aspect of protection is error confinement, without which most of the reliability goals are difficult to achieve. In this paper the problem of protecting information is analyzed in its general aspects, and the two most relevant implementation techniques are outlined, i.e., access control lists and capability ~lists. The importance of protecting memory segments is emphasized, and the implementation of a capability based addressing is investigated in particular. Two important multiprocessor systems implementing a capability based addressing are briefly described.