Our software does not support change the identity of a CA when you issue it a 
new certificate. I assume that this is similar issuing passports. When an 
individual gets a passport they put their identity in the passport, when they 
renew their passport, they use the same identity.

We do use CNs for subordinate CAs and the CNs are unique per CA. We do not use 
unique CNs per CA certificate.

Please also note that the unique CN is also for a unique private key.

Bruce.

From: Ryan Sleevi [mailto:[email protected]]
Sent: Wednesday, April 26, 2017 1:53 PM
To: CA/Browser Forum Public Discussion List <[email protected]>
Cc: Gervase Markham <[email protected]>; Bruce Morton 
<[email protected]>
Subject: Re: [cabfpub] [EXTERNAL]Re: Ballot 199 - Require commonName in Root 
and Intermediate Certificates



On Wed, Apr 26, 2017 at 1:25 PM, Bruce Morton via Public 
<[email protected]<mailto:[email protected]>> wrote:
Hi Gerv,

I'm also confused with the proposal, so wanted to discuss our methodology.

From our point of view, we create a subordinate certification authority and 
give this CA a distinguished name. We use the CN to give the CA a unique 
identifier, so that the common name will not be mixed up with any other 
subordinate CAs.

Then we need to give the subordinate CA trust, so we issue it a subordinate CA 
certificate from a root CA. The subordinate CA certificate will have the same 
distinguished name.

All fantastic so far...

If for some reason we need to issue the subordinate CA another CA certificate 
(e.g., the original certificate expires), then the new certificate will have 
the identical subject name as the original.

Could you explain the use cases here? This introduces a significant amount of 
complexity (ergo: risk) into the Web PKI. The situation you described - the 
original expiring - should not require the reissuance with the same name, 
because no leaf certificate should have exceeded the validity window of the 
intermediate. As you approach the intermediates expiration, minimally, you 
could/should have begun transitioning off of it.

What other use cases exist to imbue this? I can certainly understand situations 
like "add additional extensions", but there again, a new name (for new 
certificates) could imbue the new powers and capabilities. The only reason to 
reissue the existing certificate is to retroactively imbue the extant 
certificates with new capabilities, and I'm curious when that situation is 
necessary.

Otherwise, it should hopefully seem uncontroversial to identify a new common 
name for this new certificate with new capabilities (whether the validity 
period or the extension-based capability). But I'm interested to learn why CAs 
do so, and if there's any particular need/advantage over simply issuing a new 
intermediate.
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