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Re: [saag] height of PKI

Russ Housley <housley@vigilsec.com> Wed, 26 August 2020 14:44 UTC

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From: Russ Housley <housley@vigilsec.com>
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To: Michael Richardson <mcr+ietf@sandelman.ca>
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Subject: Re: [saag] height of PKI
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> On Aug 25, 2020, at 11:14 PM, Michael Richardson <mcr+ietf@sandelman.ca> 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.

Russ

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