Re: [Rats] Composite Evidence

Michael Richardson <> Thu, 23 January 2020 02:40 UTC

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From: Michael Richardson <>
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Date: Wed, 22 Jan 2020 21:40:29 -0500
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Subject: Re: [Rats] Composite Evidence
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Eric Voit (evoit) <> wrote:
    > I promised you a definition for Composite Evidence.  You can see my proposed
    > definition directly the text below, but I am not willing yet to place
    > it in a
    > Pull Request. I thought an email thread might be helpful first.

First, I found the diagram confusing, because I think you rotated our
previous diagram 90 degress clockwise.
The Verifier A, was in my mind, towards me (in the third dimension) out,
"above" the "Internal Verifier", which we asked to have renamed "Claims Collector"
(Screw the monochrome SVG debate... lets go VRML)

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

    > Anyway my strawman definition for Composite Evidence is:  Evidence which
    > includes multiple sub-elements of evidence, more than one of which can be
    > computationally verified to have been generated by a specific Attester
    > Subcomponent or Verifier.

I am not sure what "computationally" verified means.
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?)

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[];
2) struct attestation_results foo[];

but rather:
    union composite_evidence {
          struct evidence_claims ec;
          struct attestation_results ar;
    } foo[];

were I more hip, I'd learn to write this in CDDL.

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