Subject: draft liaison response re DR 320

From: Stephen Kent <[email-masked]>
Date: Mon, 10 Dec 2007 10:31:05 -0500

Folks,

Since there has been a lot of discussion on this 
topic, I wanted to share the current draft of a 
formal response to ITU-T re DR 320.

Steve
-----

Gentlemen:

This is a response to your communiqué of 
2007-10-05 re Defect Report 320 submitted to 
ITU-T SG17.

The PKIX Working Group met in Vancouver on 
2007-12-03 and discussed your message and DR 320. 
We agree that the X.500 model, and X.501 
specifically, defines a DN as a globally unique 
identifier in The Directory. As you noted, name 
uniqueness is a critical feature of hierarchic 
distributed naming schemes, such as X.500 and the 
DNS, and for e-mail addresses. In the Internet we 
have successfully dealt with the problem of name 
uniqueness for DNS names and, as a corollary, for 
RFC 822 e-mail addresses. However, it has 
required a substantial investment of resources 
over about 25 years to achieve our current status 
in this regard. Unfortunately, the X.500 
directory model, perhaps in part because of its 
richer naming semantics, has not achieved the 
same status.  It often is not an easy task for a 
CA to examine a proposed name and determine if 
the Subject has the right to that name, when the 
name is a DN.

Thus we agree with the observations made in DR 
320. It is a fact that Certification Authorities 
(CAs) are being deployed with names chosen 
locally, without acquiring a DN from a naming 
authority. It also is true that the IETF provides 
no guidance to CAs on how to choose names that 
are unambiguous, or on how CAs might coordinate 
on global scale to avoid name collisions for 
themselves and for the entities to whom they 
issue certificates.

We have discussed this matter in the PKIX Working 
Group, and have consulted with the Security Area 
Directors and the with IETF Chair. We do not 
anticipate that PKIX nor any other working group 
in the IETF will take any action to address this 
problem. Thus, for example, we do not plan to 
establish a list of DNs of extant CAs to be 
checked by prospective CAs.

---

From: Denis Pinkas <[email-masked]>
Date: Thu, 13 Dec 2007 10:09:58 +0100

See a change proposal in the middle of the text.

> Folks,
>
> Since there has been a lot of discussion on this topic, I wanted to 
> share the current draft of a formal response to ITU-T re DR 320.
>
> Steve
> -----
>
> Gentlemen:
>
> This is a response to your communiqué of 2007-10-05 re Defect Report 
> 320 submitted to ITU-T SG17.
> The PKIX Working Group met in Vancouver on 2007-12-03 and discussed 
> your message and DR 320. We agree that the X.500 model, and X.501 
> specifically, defines a DN as a globally unique identifier in The 
> Directory. As you noted, name uniqueness is a critical feature of 
> hierarchic distributed naming schemes, such as X.500 and the DNS, and 
> for e-mail addresses. In the Internet we have successfully dealt with 
> the problem of name uniqueness for DNS names and, as a corollary, for 
> RFC 822 e-mail addresses. However, it has required a substantial 
> investment of resources over about 25 years to achieve our current 
> status in this regard. Unfortunately, the X.500 directory model, 
> perhaps in part because of its richer naming semantics, has not 
> achieved the same status.  It often is not an easy task for a CA to 
> examine a proposed name and determine if the Subject has the right to 
> that name, when the name is a DN.

I propose to delete the following sentence, since we do not agree with 
all the observations made in DR 320.

> Thus we agree with the observations made in DR 320.

> It is a fact that Certification Authorities (CAs) are being deployed 
> with names chosen locally, without acquiring a DN from a naming 
> authority.

This sentence is very important and its consequences should be 
mentionned. I propose to add the following text:

"As a consequence, nothing may prevent two unrelated CAs to choose the 
same DN for two different entities (e.g. end-entities, CAs, CRL Issuers, 
OCSP responders). By implication, a CA DN and a serial number taken 
alone do not necessarilly identify a single entity".

> It also is true that the IETF provides no guidance to CAs on how to 
> choose names that are unambiguous, or on how CAs might coordinate on 
> global scale to avoid name collisions for themselves and for the 
> entities to whom they issue certificates.
>
> We have discussed this matter in the PKIX Working Group, and have 
> consulted with the Security Area Directors and the with IETF Chair. We 
> do not anticipate that PKIX nor any other working group in the IETF 
> will take any action to address this problem. Thus, for example, we do 
> not plan to establish a list of DNs of extant CAs to be checked by 
> prospective CAs.

---

From: Russ Housley <[email-masked]>
Date: Thu, 13 Dec 2007 11:19:11 -0500

Denis:

>>Gentlemen:
>>
>>This is a response to your communiqué of 2007-10-05 re Defect 
>>Report 320 submitted to ITU-T SG17.
>>hierarchic distributed naming schemes, such as X.500 and the DNS, 
>>and for e-mail addresses. In the Internet we have successfully 
>>dealt with the problem of name uniqueness for DNS names and, as a 
>>corollary, for RFC 822 e-mail addresses. However, it has required a 
>>substantial investment of resources over about 25 years to achieve 
>>our current status in this regard. Unfortunately, the X.500 
>>directory model, perhaps in part because of its richer naming 
>>semantics, has not achieved the same status.  It often is not an 
>>easy task for a CA to examine a proposed name and determine if the 
>>Subject has the right to that name, when the name is a DN.
>
>I propose to delete the following sentence, since we do not agree 
>with all the observations made in DR 320.
>
>>It is a fact that Certification Authorities (CAs) are being 
>>deployed with names chosen locally, without acquiring a DN from a 
>>naming authority.
>
>
>"As a consequence, nothing may prevent two unrelated CAs to choose 
>the same DN for two different entities (e.g. end-entities, CAs, CRL 
>Issuers, OCSP responders). By implication, a CA DN and a serial 
>number taken alone do not necessarilly identify a single entity".

This is not the whole story.  We have requirements about the CRL and 
certificate signer certificates chaining to the same trust 
anchor.  To me, this significantly reduces the concerns.

Russ

---

From: Stephen Kent <[email-masked]>
Date: Mon, 17 Dec 2007 16:07:32 -0500

At 10:09 AM +0100 12/13/07, Denis Pinkas wrote:
>...

I have already changed the text to reflect the fact that we agreed 
with the two points from DR 320 that were cited in the liaison 
message, not with all of DR 320. This was triggered by David Kemp's 
message of 12/10 re the draft meeting minutes, and is illustrated in 
my response to his message, posted on 12/11.

>number taken alone do not necessarilly identify a single entity".

I don't think we need to provide this explanation of the implications.

Steve