lecture_3_part_2

In some circumstances easy model for transfer of

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Unformatted text preview: + Easy model for transfer of privileges – Hard to determine who can access an object – Requires extra mechanism to allow revocation – In network environment, need cryptographic methods to prevent forgery CS 236 Online Lecture 3 Page 11 ACLs, Capabilities, Complete Mediation, & Performance • Ideally, every data access should have access control independently applied • Practicality of doing so depends on the performance costs • What does it cost to use ACLs? – Capabilities? CS 236 Online Lecture 3 Page 12 Performance Issues of Access Control • What if the status of the access control mechanism changed between when last checked and current access? • Common case is nothing changes • Different approaches possible – Actually check changeable data structure on each access – Give process something cheap and revocable that allows access CS 236 Online Lecture 3 Page 13 Access Control in the Distributed World • ACLs still work OK – Provided you have a global namespace for subjects – And no one can masquerade • Capabilities are more problematic – Their security relies on unforgeability CS 236 Online Lecture 3 Page 14 Using Cryptographic Capabilities • Can cryptography make...
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