Subject: RE: cA Flag -- cRLSign

From: Santosh Chokhani <[email-masked]>
Date: Thu, 24 May 2001 17:01:09 -0400

Steve:
 
I vote for not requiring the cA flag for CRL check and making appropriate
changes to X.509 and to PKIX to make it clear and consistent
 
-----Original Message-----
From: Stephen Kent [mailto:[email-masked]]
Sent: Tuesday, May 22, 2001 8:13 AM
To: Santosh Chokhani
Cc: [email-masked]
Subject: Re: cA Flag -- cRLSign

At 2:55 PM -0400 5/18/01, Santosh Chokhani wrote:

Steve:

I have a compromise proposal in this area.  As Russ Housley says: In the
interest of interoperability, the generator should be strict and processor
should be forgiving (assuming no security) is compromised.

I would say let us do the following:

1.  A PKIX compliant CA must assert basicConstraints with cA set to TRUE if
cRLSign bit is set, and

2.  A PKIX compliant relying party client must check cRLSign flag in the
keyUsage extension, if keyUsage extension is present, when using the public
key of the subject to verify a signature on the CRL.  However, if the
keyUsage extension is absent, basicConstraints must be present with cA =
TRUE

I think it confusing for a standard to encourage asymmetric behavior for CAs
vs. clients. It also removes a big part of the motivation for CAs to set the
flag according to the standard.

As I said earlier, if there is consensus to remove the need for cA to be
asserted in certs associated with CRL validation, then we can make that
explicit in the standard, but we just have to "buy in" to making the other
changes to clarify this, and to name a role for entities who sign CRLs but
who are not CAs.

Steve