I am reading CISSP and more specifically the Biba model. Biba has some basic properties:

  • The Simple Integrity Property states that a subject cannot read an object at a lower integrity level (no read-down).
  • The * (star) Integrity Property states that a subject cannot modify an object a a higher integrity level (no write-up).

I am a little confused about the first property.


The idea of the "no read down" principle is simply that information produced at a lower level may be tainted, and should not be consumed by a member of a higher tier in the hierarchy.

A classical example is that a priest may write a prayerbook for a farmer, but should not accept religious ideas from the farmer.

  • 2
    The reason for this is to avoid someone from a higher integrity level being corrupted by something written at a lower level. It prevents bias, and less reputable information from being accidentally re-published by a more reputable author than the source material deserves. – Daisetsu Dec 2 '18 at 21:56

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