Subject: RE: Logotypes in certificates

From: Ambarish Malpani <[email-masked]>
Date: Wed, 21 Mar 2001 09:06:35 -0800

Steve,
    This is the same argument as a CA issuing a cert to a
subordinate, who issues incorrect certificates with it - e.g.
issues a certificate for the domain www.amazon.com to say BN.

Either a CA controls/audits subordinate CAs, or has enough
reason to trust them, or the value of that hierarchy is
pretty useless.

I don't think logos in certificates affect this either way.

Regards,
Ambarish

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Ambarish Malpani
Architect                                                650.567.5457
ValiCert, Inc.                                  [email-masked]
339 N. Bernardo Ave.                          http://www.valicert.com
Mountain View, CA 94043

> -----Original Message-----
> From: Stephen Kent [mailto:[email-masked]]
> Sent: Tuesday, March 20, 2001 8:57 PM
> To: Dean Povey
> Cc: [email-masked]
> Subject: Re: Logotypes in certificates
> 
> 
> Dean and Stefan,
> 
> As a security kinda' guy, I always approach this from the "what will 
> the bad giy do" perspective.  From that perspective, I worry that a 
> TTP CA will cerfity company X, putting the company X logo in the 
> cert. Then company X will issue a cert to a subordinate CA, and put 
> in that cert an inappropriate logo. It is not realistic for an app to 
> display a chain of logos, and expect a user to pay attention, any 
> more that if one displayed a chain of DNs.  I still maintain that we 
> can agree on what would be a reasonable set of circumstances in which 
> the logo extension would be useful and safe, but I don't see a 
> technical means of enforcing these circumstances without changes to 
> the path validation algorithm. I am open to suggestions that provide 
> the necessary controls and don't have this unfortunate side effect, 
> but I have yet to see an example of such.
> 
> Steve
>

---

From: [email-masked] (Terry Hayes)
Date: Wed, 21 Mar 2001 09:55:48 -0800

Ambarish,

I think that Steve is after a technical method to restrict the types of 
certificates that a subordinate CA can issue.  You can, as you point 
out, use legal methods and auditing to do this, but in some cases it may 
be better to have a technical solution that makes incorrect certificates 
invalid, or not useful.

Name constraints is one such technical means.  Using it we can restrict 
the names in certificates to a particular DN subset, or to a particular 
DNS domain.  It won't help with the case you give, but it does allow 
delegation of authority to a CA for valicert.com or netscape.com (for 
example!)

One possible technical solution for logtypes is the certificate policies 
extension.  By defining application level processing to require a 
certain certificate policy in the certificate (or one of a set of 
policies), the application can be confident that the trust point (root 
CA) has granted authority to include logotypes in the certificate.  
certificate policies has the correct hierarchical structure and 
processing rules to enforce this.

Terry

---

From: Stephen Kent <[email-masked]>
Date: Wed, 21 Mar 2001 17:59:50 -0500

Ambarish,

>I don't think logos in certificates affect this either way.

No, the argument is not the same.  We have the nameConstraints 
extension as a technical means of preventing a CA and subordinate CAs 
from issuing certs with names outside of a well defined range. We do 
not have a means to enforce similar controls re logos. That's the 
whole point of my concern.

Steve