Subject: RE: keyCertSign and cRLSign Key Usage Bits

From: Ambarish Malpani <[email-masked]>
Date: Tue, 24 Apr 2001 10:55:20 -0700

I agree, also.

Ambarish

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

-----Original Message-----
From: Santosh Chokhani [mailto:[email-masked]]
Sent: Tuesday, April 24, 2001 8:22 AM
To: Housley, Russ; [email-masked]
Subject: RE: keyCertSign and cRLSign Key Usage Bits

Russ: I agree with the text. 

I also know that Steve Kent and Sharon Boeyen feel that X.509 states that
only CA can issue CRL (the context of my comments being PKI only and not
PMI).

But, using the theory that you suggest that the client be forgiving, I would
consider a client compliant if it did NOT check the basic constraint
extension while verifying a signature on a CRL.  It need to ensure that the
cRLSign bit is set in the keyUsage extension.

-----Original Message----- 
From: Housley, Russ [ mailto:[email-masked]
<mailto:[email-masked]> ] 
Sent: Tuesday, April 24, 2001 10:37 AM 
To: [email-masked] 
Subject: keyCertSign and cRLSign Key Usage Bits 

The consensus on these bits is not totally clear to me.  Yet, several 
points have been consistently, and I think that the following text 
incorporates them.  The debate regarding he linkage between these bits and 
the cA bit in the basic constraints extension does not seem to be over, and 
I have not made any changes in that area.  Please use this new thread to 
discuss any remaining unresolved points. 

       The keyCertSign bit is asserted when the subject public key is 
       used for verifying a signature on public key certificates.  This 
       bit MUST only be asserted in CA certificates.  If the keyCertSign 
       bit is asserted, then the cA bit in the basic constraints 
       extension (see 4.2.1.10) MUST also be asserted.  If neither the 
       cRLSign bit nor the keyCertSign bit are asserted, then the cA bit 
       in the basic constraints extension MUST NOT be asserted. 

       The cRLSign bit is asserted when the subject public key is used 
       for verifying a signature on a certificate revocation list (e.g., 
       a CRL or an ARL).  This bit MUST be asserted in CA and Attribute 
       Authority (AA) certificates that are used to verify signatures on 
       CRLs.  If the cRLSign bit is asserted in a CA certificate, then 
       the cA bit in the basic constraints extension (see 4.2.1.10) MUST 
       also be asserted.  If the cRLSign bit is asserted in a AA 
       certificate, then the cA bit in the basic constraints extension 
       MUST NOT be asserted.  Such AA certificates MUST NOT be used to 
       verify signatures on CRLs containing revocation information for 
       public key certificates; however, these AA certificates MAY be 
       used to verify signatures on CRLs containing revocation 
       information concerning attribute certificates.  If neither the 
       cRLSign bit nor the keyCertSign bit are asserted, then the cA bit 
       in the basic constraints extension MUST NOT be asserted. 

Russ

---

From: Stephen Kent <[email-masked]>
Date: Wed, 25 Apr 2001 15:50:45 -0400

>Ambarish

I disagree. We need to make a decision on whether a cert without a CA 
flag enabled can sign CRLs. If so, then we need to modify a lot of 
text in 2459, and in X.509, to say this clearly. Suggesting that a 
client be "forgiving" in this context is not a viable proposal for a 
standard.

Steve
>339 N. Bernardo Ave.                          
><http://www.valicert.com/>http://www.valicert.com
>Mountain View, CA 94043
>
>I also know that Steve Kent and Sharon Boeyen feel that X.509 states 
>that only CA can issue CRL (the context of my comments being PKI 
>only and not PMI).
>
>But, using the theory that you suggest that the client be forgiving, 
>I would consider a client compliant if it did NOT check the basic 
>constraint extension while verifying a signature on a CRL.  It need 
>to ensure that the cRLSign bit is set in the keyUsage extension.
>
>From: Housley, Russ 
>[<mailto:[email-masked]>mailto:[email-masked]]