[cabfpub] For Discussion: S/MIME Working Group Charter

Tim Hollebeek tim.hollebeek at digicert.com
Thu May 24 05:57:21 MST 2018

Yeah, I want something focused.  There are lots of different clientAuth use cases, not just individual identity.  clientAuth only looks like emailProtection if you’re limiting yourself to the use cases where there’s strong overlap.  Which makes the argument that they are similar essentially a tautology.  Remember, clientAuth can also be mutual authentication for web services.  That looks nothing like emailProtection.


So let’s get email on a firm footing first, and if the section of the clientAuth BRs for individuals is heavily based on the emailProtection BRs, that just saves us work in the future.




From: Public [mailto:public-bounces at cabforum.org] On Behalf Of Dimitris Zacharopoulos via Public
Sent: Thursday, May 24, 2018 1:05 AM
To: Moudrick M. Dadashov <md at ssc.lt>; Brown, Wendy (10421) <wendy.brown at protiviti.com>; CA/Browser Forum Public Discussion List <public at cabforum.org>; Ryan Sleevi <sleevi at google.com>
Subject: Re: [cabfpub] For Discussion: S/MIME Working Group Charter


Moudrick, I don't think we are describing just use scenarios. This is about subject validation and as you are very well familiar, eIDAS is also setting requirements for how you validate natural persons and legal entities. Then, you can use this validated information for different trust services (authenticate, sign, encrypt, etc).

We already have identity validation requirements for the server certificate Working Group, described in DV/OV/EV Policies for certificates with id-kp-serverAuth EKU. Why shouldn't we include identity validation requirements for this new Working Group for certificates with id-kp-clientAuth and id-kp-emailProtection EKU? The overlap in subject validation requirements between these two cases is pretty obvious.

Even though I'd like the clientAuth to be included in the WG's initial charter, I understand Ryan's argument for gradually building a standard with minimum expectations at the beginning (thus limiting the scope for S/MIME only) and expand the scope later. 

So, until then, the clientAuth Certificates will remain kind-of "unregulated" by lacking a policy standard. I suppose we will have to live with that :)


On 24/5/2018 2:34 πμ, Moudrick M. Dadashov wrote:

All three (clentAuth and S/MIME) use scenarios are essentially different.

Validation requirements for issuing signing/encryption certificates are mostly similar, clientAuth (as we understand it under eIDAS*) is different.


* Article 3
(5) ‘authentication’ means an electronic process that enables the electronic identification of a natural or legal person, or the origin and integrity of data in electronic form to be confirmed.

(1) ‘electronic identification’ means the process of using person identification data in electronic form uniquely representing either a natural or legal person, or a natural person representing a legal person.

(2) ‘electronic identification means’ means a material and/or immaterial unit containing person identification data and which is used for authentication for an online service.


On 5/24/2018 12:16 AM, Brown, Wendy (10421) via Public wrote:

I second the opinion that  clientAuth and S/Mime are likely to have a great overlap in validation requirements at least when issuing to persons and PKIs may want to issue both types of certs from the same CA if they are for the same validated individual..


From: Public [mailto:public-bounces at cabforum.org] On Behalf Of Ryan Sleevi via Public
Sent: Friday, May 18, 2018 9:18 AM
To: Dimitris Zacharopoulos  <mailto:jimmy at it.auth.gr> <jimmy at it.auth.gr>; CA/Browser Forum Public Discussion List  <mailto:public at cabforum.org> <public at cabforum.org>
Subject: Re: [cabfpub] For Discussion: S/MIME Working Group Charter




On Fri, May 18, 2018 at 12:57 AM, Dimitris Zacharopoulos via Public <public at cabforum.org <mailto:public at cabforum.org> > wrote:


On 18/5/2018 2:51 πμ, Ryan Sleevi via Public wrote:

I don't think it's a cross-EKU situation, though, but I'm glad we're in agreement. 


An email server certificate is an id-kp-serverAuth EKU. That's already covered by another WG

I sincerely hope that id-kp-clientAuth EKU will also be covered by this WG since there will be common validation requirements for Subject information, as with S/MIME. It seems too much overhead to spawn an entirely different WG to deal just with clientAuth.

If people agree, how about using the name "Client and S/MIME Certificate WG" which seems aligned with the "Server Certificate WG"?


As I've mentioned several times, it would be good to actually focus on a constrained, defined problem, before you proverbially try to boil the ocean.


It is not obvious that there will be common validation requirements, because the id-kp-clientAuth situation has a vast dimension of possible uses and spectrum. It's not actually reflective of the deployed reality that the validation requirements are the same. It also is based on an entirely separate notion of identity.


So no, I don't agree, because they really are substantially different in deployed reality - and an S/MIME WG is, in itself, a sizable undertaking just to get S/MIME BRs, due to the broad spectrum of client capabilities and CA past-practices - and the lifetime of extant certificates that presents unique challenges to defining a sensible and realistic profile.


A good charter - one that leads to productive engagement from a broad set of participants while actually delivering meaningful improvements - is one that keeps itself narrowly focused on the task at hand, produces results, and then looks to recharter based on the things you knew were out there, but agreed not to discuss until you actually completed the work. That allows you to keep momentum, focus, and participation. Just look at the challenges each of our (legacy) WG has faced with a broad remit, in that the set of topics has made it difficult both to engage participation of the broader Forum and to actually make forward progress, because it's constantly having to deal with 'all these things' or trying to do 'all these things'.


When we see narrowly focused ballots and efforts that try to solve a specific set of problems, then we make progress. The validation WG's effort at is a prime example of that - a prolonged effort that directly benefited from being focused on that problem, and ruling some things (like out of scope of the discussion in order to make progress on the narrow set.


The same too is in the charter. Let's not try to encompass pet marketing projects (EV for S/MIME), "things we might need but we don't know why" (network security), or "things that are kinda related, but only in some domains" (id-kp-clientAuth). Let's focus on the problem at hand - S/MIME authentication - keeping the WG scoped narrowly and on task, and deliver something that can help users have faith in the Web PKI to deliver tangible benefits in that space, rather than the reality we have today.

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