Subject: AKI and AuthorityCertIssuer

From: "Wang, John" <[email-masked]>
Date: Mon, 21 Dec 1998 18:56:45 -0500

Tim,

I believe PKIX Part 1 is a bit misleading when describing AKI's
AuthorityCertIssuer. The text of the extension description
states:

|| The identification may be based on either the key identifier
|| (the subject key identifier in the issuer's certificate) or on
|| the issuer name and serial number.

The ASN.1 definition farther down in the standard lists the
components as:

|| authorityCertIssuer       [1] GeneralNames            OPTIONAL,
|| authorityCertSerialNumber [2] CertificateSerialNumber OPTIONAL  }

There has been a lot of confusion as to whether "issuer name" is
really the "issuer name" or the "issuer's issuer name." I believe
it has to be the latter case because the certificate already has the
issuer name so adding that to AKI provides no additional value.
Adding "issuer's issuer name" and "issuer serial number" however,
provides the missing link to the issuing certificate.

I would like to see the sentence restated similar to:

|| The identification may be based on either the key identifier
|| (the subject key identifier in the issuer's certificate) or on
|| the issuer's issuer name and issuer's serial number.

I've chosen "issuer's issuer name" because "authorityCertIssuer" seems
to lead to some confusion even though authority means the cert that
issued the cert with the AKI extension. Thus, "authorityCertIssuer"
should mean the signing CA's issuer.

One problem with the current definition is that using just "issuer
name" instead of "issuer's issuer name" works when verifying against
certificates issued directly off self-signed CA where IDN = SDN. Thus,
implementors that only test against self-signed CA's may conclude
they have a proper implementation, when in fact, it only works by
coincidence.

I have confirmed with Steve Kent that "issuer's issuer name" is what
is intended for the authorityCertIssuer field.

Regards,

John

John Wang              | GTE Internetworking      | Tel: 781-455-5896
Technical Specialist   | 77 'A' Street, MS 03-41  | Fax: 781-455-4015
CyberTrust Solutions   | Needham, MA  02494-2892  |
[email-masked]

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From: Brian Korver <[email-masked]>
Date: Mon, 21 Dec 1998 21:35:09 -0800

> provides the missing link to the issuing certificate.

You are correct, it is the "issuer's issuer name".

> || the issuer's issuer name and issuer's serial number.

How about "...the issuer name and serial number of the issuer's
certificate" instead?  And perhaps with a clarifying comment
"(the CA certficate that issued the certificate that the AKI
extention appears in)"?