Subject: RE: Request change in son-of-rfc2633

From: [email-masked] (Peter Gutmann)
Date: Tue, 28 Oct 2003 14:32:28 +1300

"Blake Ramsdell" <[email-masked]> writes:

>S/MIME v3.1 implementations MUST allow for the use of the choice of
>subjectKeyIdentifier in messages.

Given the recent debate over the use of keyIDs on the PKIX list, shouldn't
this be:

  S/MIME vAnything MUST NOT rely on the use of subjectKeyIdentifier in
  messages.

Peter.

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From: "Blake Ramsdell" <[email-masked]>
Date: Mon, 27 Oct 2003 17:55:18 -0800

> -----Original Message-----
> From: Peter Gutmann [mailto:[email-masked]] 
> Sent: Monday, October 27, 2003 5:32 PM
> To: [email-masked]; [email-masked]; 
> [email-masked]
> Cc: [email-masked]
> Subject: RE: Request change in son-of-rfc2633
> 

My understanding of the discussion is that there could be multiple
certificates with the same SKI.  Do we need to clarify our language to
warn that there might be multiple certificates that match a particular
SKI, and you should just try out each one until you find one that works?
We'll probably need to discuss the implications of this.

Apparently I was one of the deluded folks that believed that SKI was
meant to be globally unique.

Blake

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From: Russ Housley <[email-masked]>
Date: Tue, 28 Oct 2003 08:47:08 -0500

I disagree.  Key identifiers are much smaller than <issuer distinguished 
name, serial number>. When the key identifiers are computed from the public 
key (as is recommended by RFC 3280), the likelihood of collision is 
acceptably small. Further, if there is a collision, an implementation can 
try the very small number of public keys that have the same identifier.

Russ

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From: "Blake Ramsdell" <[email-masked]>
Date: Tue, 28 Oct 2003 14:44:05 -0800

> From: Russ Housley [mailto:[email-masked]] 
> Sent: Tuesday, October 28, 2003 5:47 AM
> To: Peter Gutmann; [email-masked]; 
> [email-masked]; [email-masked]
> Cc: [email-masked]

I think that the direction that's on the table is to clarify that
lookups by SubjectKeyIdentifier may yield more than one certificate, and
implementations should be prepared for that and not freak out and panic
the user.

Blake

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From: Russ Housley <[email-masked]>
Date: Tue, 28 Oct 2003 18:19:49 -0500

No problem.