Access Control - E-Commerce - Lecture Slides, Slides of Fundamentals of E-Commerce

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Access Control Lists S\O OperatingAccountssystemprogram

AccountiAudit trailng data Sam^ rwx^ rwx

rw^ r Alice^ x^ x

rw^ - Bob^ rx^ r

r^ r

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Discretionary and Nondiscretionary

Access

Controls (DAC & MAC)
Discretionary means that someone who owns aresource can make a decision as to who isallowed to use (access) it
Nondiscretionary (mandatory) access controlsenforce a policy where users might be allowed touse information themselves but might not beallowed to make copy of it available to someoneelse (even the owner cannot change the attributeof a data file)

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Multi-level model of security
Security labels:^ TOP SECRET^ SECRET^ CONFIDENTIAL^ OPEN
Both subjects and objects have security labels
Only subjects with the proper clearance (securitylabel) can see the objects with the same or lowerlevel of security labels

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Information Flow control
Bell LaPadula (BLP) model
Simple security property: no read up
*-property: no write down

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Covert channels (cont.)
The timing channel – The Trojan horse program alternatelyloops and waits, in cycles of, say one minute per bit (of theconfidential data). When the bit is 1: the program loops for oneminute. When the bit is 0: the program waits for a minute.Another program running on the same computer (but withoutaccess to the sensitive data) constantly tests the loading of theTrojan horse.
The storage channel – The Trojan horse program loads a(printer) queue to represent a 1, and delete its jobs to represent a0. Easy to check the queue status and get the information.
The error channel – The Trojan horse program creates a file torepresent a 1, and delete it to represent a 0. The external processtries to read the file: since different error messages are reportedwhen the file exists (but its access is not permitted) or when thefile does not exist, which are used to distinguish between the 0'sand 1's.

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The Orange Book
The National Computer Security Center (NCSC)published an official standard called “TrustedComputer System Evaluation Criteria” (theOrange Book) which defines a series of ratings acomputer system can have based on its securityfeatures and the care that went into its design,documentation, and testing