Subject: Re: Dedicated CRL signing keys

From: Russ Housley <[email-masked]>
Date: Wed, 18 Apr 2001 17:07:37 -0400

Trevor:

I propose the following solution that builds on the Indirect CRL 
capabilities that are already available.  When a CA wants to employ 
separate private keys to sign certificates and CRLs, then that CA MUST 
delegate CRL signing to a separate authority.  That separate authority MUST 
have a different Distinguished Name that the CA, but it could be operated 
by the same organization.  In this way, the IDP CRL extension would flag 
the "unusual" circumstances.  Clients that do not support Indirect CRLs can 
fail gracefully (unsupported optional feature), and clients that support 
Indirect CRLs can happily handle the certificates and CRLs.

Thoughts?

Russ

At 01:32 PM 4/18/2001 -0700, Trevor Freeman wrote:
>There has been some discussion regarding the proposal to have CRLs
>signed with CA keys which do not also sign certificates. Since this will
>not be a mandatory to implement feature, I am concerned about the impact
>on pkix compliant clients who encounter CRL signed in this way, and how
>we expect them to behave. What seem unacceptable with the current
>proposal is that the signage check on the CRL will fail, and the client
>will have little clue as to why and if this failure is expected. The
>information in the chain, while present, is in the CAs certificate, is
>difficult to find and subtle so would be easily missed by someone
>debugging this problem. I would like to see some clearer indication in a
>critical extension in the CRL itself that would indicate what was going
>on. In expressing these semantics in a critical extension, we maintain
>the principal that if you don't understand the extension, the client
>knows to fail due to its own inadequacies and that failure is by design,
>therefore allowing the client's to return an error unsupported option
>rather than invalid signature.
>Trevor

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From: Juergen Brauckmann <[email-masked]>
Date: Thu, 19 Apr 2001 08:52:34 +0200

Russ Housley wrote:
> have a different Distinguished Name that the CA, 

Why must it have a different DN?

Regards,
   Juergen

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From: Stephen Farrell <[email-masked]>
Date: Thu, 19 Apr 2001 15:06:49 +0100

Russ,

That'd be a bad resolution since it would break deployed CAs who
use the same name and different cert and CRL signing keys (and
those do exist and are operating).

Any other ideas or should we just require clients to understand
what's going on based on key usage?

Stephen.

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