Computer Security

this report it is trusted to meet the security specifications. In some other context it might be trusted to control a shuttle launch or to retrieve all the 1988 court opinions dealing with civil rights. People concerned about security have tried to take over the word `trusted' to describe their concerns; they have had some success because security is the area Policies are often called `requirements'; sometimes the word `policy' is reserved for a broad statement and `requirement' is used for a more detailed one in which the most effort has been made to specify and build trustworthy systems. We will adopt this usage, while recognizing that in a broader context `trusted' may have many other meanings. Policies express a general intent. Of course, they can be more detailed than the very general ones given as examples above; for instance, here is a refinement of the first policy: Salary secrecy: Individual salary information shall only be disclosed to the employee, his superiors, and authorized personnel people. But whether general or specific, policies contain terms which are not precisely defined, so it isn't possible to reliably tell whether a system satisfies them. Furthermore, they specify the behavior of people and of the physical environment as well as the behavior of machines, so it isn't possible for a computer system alone to satisfy them. Technology for security addresses these problems by providing methods for: Integrating a computer system into a larger system, comprising people and a physical environment as well as computers, that meets its security policies. Giving a precise specification, called a security model, for the security-relevant behavior of the computer system. Building a system that meets the specifications out of components that provide and use s..