Re: [Rats] Composite Evidence

Michael Richardson <mcr+ietf@sandelman.ca> Thu, 23 January 2020 20:26 UTC

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Subject: Re: [Rats] Composite Evidence
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Eric Voit (evoit) <evoit@cisco.com> wrote:
    >> First, I found the diagram confusing, because I think you rotated our
    >> previous diagram 90 degress clockwise.

    > As I was adopting the passport model, I used the Architecture Document
    > Figure 4 in Section 5.1 as a base.

Yes, I knew that, but I think we need to meld it into the diagram we have,
so we need to find a way to allow people's visual cortex to map things visually.

    >> Second, I found the extra hash(),@time, stuff distracting, as it went into
    > a
    >> level of detail that just confused me.

    > I need to put together a submission which defines the elements diagram.
    > These details are important for exposing why I see the intersections of
    > evidence types and composite evidence being quite important.  Some of these
    > reasons are exposed in my reply to Dave & Ned which dives into three types
    > of evidence (i), (ii), & (iii).

I'm happy if you have "ev(i)","ev(ii)", etc. and explain that in the text.

    >> Give an example of something that would not fall into that category.
    >> Maybe you are trying to abstract "has a signature" to things that can be
    >> verified without a asymmetric digital signature. (KerbV Ticket?)

    > It is true I am trying to abstract away from "has a signature".   I didn't
    > want to exclude things like the possibility that Verifier B to go back to
    > Verifier A if a trust relationship hasn't been established between them yet.

How about "signature (or equivalent)"

    >> I think that the key thing that we needed to be able to say is that
    > Composite
    >> Evidence is not:
    >> 1) struct evidence_claims foo[];
    >> -or-
    >> 2) struct attestation_results foo[];
    >>
    >> but rather:
    >> union composite_evidence {
    >> struct evidence_claims ec;
    >> struct attestation_results ar;
    >> } foo[];

    > I very much agree with your code above. And the definition needs to reflect
    > this.   The question which Ned & Dave open up is whether types of
    > evidence_claims need to be exposed in your union composite_evidence.

Of course "struct evidence_claims" is a structure, I expect it to often be an EAT.
So I'm not sure I understand the debate.

    > directly hits my question of whether the definition of composite evidence
    > needs to intersect the definition of evidence types (i), (ii), & (iii).
    > The more I think about this in the context of your code above, the more I am
    > hoping to keep the two concepts orthogonal.

Is the question about how this union is distinguished?

--
]               Never tell me the odds!                 | ipv6 mesh networks [
]   Michael Richardson, Sandelman Software Works        |    IoT architect   [
]     mcr@sandelman.ca  http://www.sandelman.ca/        |   ruby on rails    [


--
Michael Richardson <mcr+IETF@sandelman.ca>ca>, Sandelman Software Works
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