v16stanford.edu-Protection_and_Security - Protection and...

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http://w w w .stanford.edu/~ouster/cgi-bin/cs140-w inter12/lecture.php?topic=protection January 11, 2012 Protection and Security Protection and Security Lecture Notes for CS 140 Winter 2012 John Ousterhout Readings for this topic from Operating System Concepts : Chapter 14, Sections 15.1-15.3, 15.5, 15.6. Protection: mechanisms that prevent accidental or intentional misuse of a system. Accidents: generally easier to solve (make them unlikely) Malicious abuse: much more difficult to eliminate (can't leave any loopholes, can't use probabilities). Three aspects to a protection mechanism: Authentication: identify a responsible party ( principal ) behind each action. Authorization: determine which principals are allowed to perform which actions. Access enforcement: combine authentication and authorization to control access. A tiny flaw in any of these areas can compromise the entire protection mechanism. Authentication Typically done with passwords : A secret piece of information used to establish identity of a user. Must not be stored in a directly-readable form: use one-way transformations. Passwords should be relatively long and obscure. Alternate form of authentication: badge or key. Does not have to be kept secret. Should not be forgable or copyable. Can be stolen, but owner will know if it is. Paradox: key must be cheap to make, hard to duplicate. Once authentication is complete, the identity of the principal must be protected from
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This note was uploaded on 04/02/2012 for the course CS 140 taught by Professor Rosenblum during the Winter '08 term at Stanford.

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v16stanford.edu-Protection_and_Security - Protection and...

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