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Re: [saag] height of PKI

Michael Richardson <mcr+ietf@sandelman.ca> Wed, 26 August 2020 21:55 UTC

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From: Michael Richardson <mcr+ietf@sandelman.ca>
To: Russ Housley <housley@vigilsec.com>
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Date: Wed, 26 Aug 2020 17:54:58 -0400
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Subject: Re: [saag] height of PKI
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Russ Housley <housley@vigilsec.com> wrote:
    >> On 2020-07-28 3:42 p.m., Benjamin Kaduk wrote:
    >>> Sorry for the clumsy description.  Basically, if you squint hard, you
    >>> could claim that at least some types of pinning are actually a PKI,
    >>> just a degenerate PKI.  E.g., in a PKI I have to pin at least one
    >>> trust anchor as the root of the PKI, and if that pinned trust anchor
    >>> just happens to also be the certificate directly used in the
    >>> protocol, it's still a PKI, just a tree of height one.
    >>
    >> I had suggested that a PKI that consisted of ROOT, Intermediate, and
    >> EE had a height of "three".  Some disagreed, and said that the EE
    >> didn't count, and it was a height of "two" Others disagreed: the EE
    >> counts, but the root doesn't count, so it's a height of "two"
    >>
    >> So is your case above a height of "one", or a height of "zero"
    >>
    >> If there is a definitive answer, I haven't found it yet.

    > You may find the description of pathLenConstraint in Section 4.2.1.9 of
    > RFC 5280 helpful.

That's interesting, but in of itself, it does not establish a zero-indexed or
one-index absolute count, as it describes an interval.

--
Michael Richardson <mcr+IETF@sandelman.ca>, Sandelman Software Works
 -= IPv6 IoT consulting =-

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