[core] Missing must in the Group OSCORE document

Jim Schaad <ietf@augustcellars.com> Sat, 01 August 2020 19:25 UTC

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From: Jim Schaad <ietf@augustcellars.com>
To: =?iso-8859-1?Q?'Christian_Ams=FCss'?= <christian@amsuess.com>, 'Marco Tiloca' <marco.tiloca@ri.se>, 'Francesca Palombini' <francesca.palombini@ericsson.com>
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Date: Sat, 1 Aug 2020 12:25:25 -0700
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Subject: [core] Missing must in the Group OSCORE document
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Christian,

 I have been thinking about the problem case of having a duplicate IV reuse
in the case where I suggested that we use separate IV spaces for the group
and pairwise keying materials.  I agree that this is a problem, however the
problem is greater than what you outlined.  This is going to be a situation
that will arise anytime that the request comes in under one security context
and the response goes out under a different security context.  In this
situation you will always have the problem that a reflected IV value from
context 1 will lead to a potential IV reuse in context 2.

Missing requirement in the document:

A server MUST use a PIV value from it's own sender context when ever it
would normally use a reflected IV, but the security context for the request
and response are not the same.

Jim