Re: How to express the TSP in SFRs for a simple encryption box
- Subject: Re: How to express the TSP in SFRs for a simple encryption box
- From: "NIAP Interpretations Board" <email@example.com>
- Date: Thu, 02 Sep 2004 13:07:29 -0700
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The NIB reminds you of two points to remember in discussing this:
1. Don't try to force things.
2. The FCS components only state what algorithms must be used for what
encryption activities; not for what purposes encryption must be used.
Thus, any solution that just has FPT_SEP, FPT_RVM, and stuff from FCS won't
work, because you never state (unless you do it via refinement) exactly what
the encryption functions are to be used for. FCS only requires that if they are
used, they satisfy certain algorithms.
The "force fit" aspect comes in with FDP_UCT. This doesn't work because there
is no flow control being done. There are no access decisions being made at all
in this; therefore the notion of an "access control" or "information flow"
policy is a force-fit.
Remember the adage: KISS (Keep It Simple...). What you express in your item
"3)": "The E(Box) receives a message from the input port and encrypt the
message, then send it out from the output port.", reworded into CC style ("The
TSF shall...") would make a fine explicitly specified requirement.
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