Steve Wang said...

>I am reading the "The CISSP Prep Guide" and have the following question
about the Biba integrity model (page 205): in the book, the simple integrity
axiom is interpreted as "no read down". why no read down for integrity?
Will read down hurt integrity?

Steve,

I had the same befuddlement at first. Try to see it this way. "Reading up"
in the context of integrity classification can do nothing but improve the
quality of your knowledge. Seen in reverse, "reading down" in the context
of integrity classification will contaminate your knowledge. By not
"writing up", you can't contaminate the knowledge of those with higher
clearances. Simplistic perhaps, but it works for me.

** VA: Security by Design **

Michael S. Arant, CISSP
Cyber Security Office (045C)
Department of Veterans Affairs, Room 352A
810 VT Ave., NW.
Washington, DC 20420
   
Voice: 202-273-8840
FAX: 202-273-6135
michael.arant@mail.va.gov
  
 -----Original Message-----
From: Steve Wang [mailto:steve.wang@entegrity.com]
Sent: Monday, October 22, 2001 12:34 PM
To: cisspstudy@lists.securityfocus.com
Subject: The Biba integrity model

Hi,

I am reading the "The CISSP Prep Guide" and have the following question
about the Biba integrity model (page 205):
in the book, the simple integrity axiom is interpreted as "no read down".
why no read down for integrity? Will read down hurt integrity?

I also saw another description of the Biba integrity model (from another
lecture) as follows
a.. Simple Integrity Property: A subject s may modify an object o only
    if the clearance of the subject dominates the classification of the
    object (this rule, no write up, is called * integrity axiom in the book)
b.. Integrity *-Property A subject s with read access to an object o can
    modify an object p only if the classification of o dominates the
    classification of p

Obviously the above statement is NOT the same (indeed it is much
different) as what is said in the book. It sounds to me that
the above one in the lecture is more reasonable.

Could somebody help me?.

Thanks,

Steve

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