PD-0048: SOF Claims for PPs without any Permutational or Probabilistic Mechanisms

This decision represents a long-term technical decision based on an OD, and may not be the same as the final results of the source OD. With respect to published criteria documentation and scheme documents, it provides suggested guidance on evaluation direction, but is not authoritative. Authoritative decisions are provided through the published criteria documents and published scheme and international interpretations thereof. With respect to published PPs, PDs are authoritative corrections to the PP, based on input from the PP author (if available), that are in force until the publication of the next revision of that PP.

Issue

In a Protection Profile, can an argument be made that the requirements for strength of function claims and analysis are unwarranted because the PP does not include any requirements that are based on permutational or probabilistic mechanisms?

Resolution

A PP author cannot predict, a priori, what mechanisms will be used to implement SFRs unless the author refines the SFRs to explicitly specify a mechanism. Thus, a Strength of Function claim must be made if AVA_SOF.1 is included as an assurance requirement. However, it is possible that a compliant ST may not contain any prob. or perm. mechanisms, thus satisfying AVA_SOF.1 vacuously.

Support

The requirements for strength of function claims and requirements stipulate that in the event that mechanisms that are permutational or probabalistic in nature are implemented to satisfy SFRs, SOF analysis must be performed, and that SOF claims for the product be stipulated. However, if such mechanisms are not included in an ST (and, in turn, in the TOE), then the requirements are satisfied trivially; no mechanisms fitting the conditions are proposed and thus no SOF claims or analysis is necessary. In short, the requirement becomes vacuous.

A PP, in general, does not include requirements for mechanisms, as claimed by the evaluators. Rather, a PP is a statement of requisite capability and behavior that can be satisfied by arbitrary mechanisms proposed by the sponsor or developer, and identified in the security target.

Note: The upcoming CCIMB rewrite of ASE (see CCIMB-INTERP-0215) will be removing the notion of an overall SOF claim.

Modification History:

2004-08-12

Updated effective date to reflect the date the PD was issued. (August 2004 NIB 6.c.xiv)

References:

• CEM p2 v1.0 APE_REQ

Related NIs:

• None

Related CCIMB-INTERPs:

• None

Source OD: 0174