Subject: Certificate for an authorized OCSP responder

From: [email-masked]
Date: Thu, 16 May 2002 14:08:10 +0200

From rfc 2560

 "The key that signs a certificate's status information need not be the
 same key that signed the certificate. It is necessary however to
 ensure that the entity signing this information is authorized to do
 so.  Therefore, a certificate's issuer MUST either sign the OCSP
 responses itself or it MUST explicitly designate this authority to
 another entity.  OCSP signing delegation SHALL be designated by the
 inclusion of id-kp-OCSPSigning in an extendedKeyUsage certificate
 extension included in the OCSP response signer's certificate.  This
 certificate MUST be issued directly by the CA that issued the
 certificate in question.

....
  They MUST reject the
   response if the certificate required to validate the signature on the
   response fails to meet at least one of the following criteria:

   1. Matches a local configuration of OCSP signing authority for the
   certificate in question; or

   2. Is the certificate of the CA that issued the certificate in
   question; or

   3. Includes a value of id-ad-ocspSigning in an ExtendedKeyUsage
   extension and is issued by the CA that issued the certificate in
   question.

.....

4.2.2.2.1  Revocation Checking of an Authorized Responder

   Since an Authorized OCSP responder provides status information for
one or more CAs "

My understanding of the RFC is that an authorized responder need more than
one certificate if it provides status information for one or more CAs otherwise
is not possible to meet the requirement that specifies the need for the
OCSP responder certificate to be issued directly from the CA that issued
the EE certificate under examination. Is this correct?

If yes it is the same true even if these different CAs belong to same PKI
?

Thanks in advance for any clarification.
Regards,
DM  

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---

From: Ambarish Malpani <[email-masked]>
Date: Thu, 16 May 2002 08:47:17 -0700

Hi DM,
    If you are trying to use the CA delegated trust model of OCSP,
then you are absolutely right - the responder will need one cert
from each CA (even if they belong to the same hierarchy).

However, if you are using the
"Matches a local configuration of OCSP signing authority for..."
model of OCSP (which I call direct trust), then you can have just
a single certificate for multiple CAs.

Hope this helps,
Regards,
Ambarish

---------------------------------------------------------------------
Ambarish Malpani
Chief Architect                                          650.567.5457
ValiCert, Inc.                                  [email-masked]
1215 Terra Bella Ave.                         http://www.valicert.com
Mountain View, CA 94043

> -----Original Message-----
> From: [email-masked] [mailto:[email-masked]]
> Sent: Thursday, May 16, 2002 5:08 AM
> To: [email-masked]
> Subject: Certificate for an authorized OCSP responder
> 
> 
> 
> From rfc 2560
>

---

From: [email-masked]
Date: Fri, 17 May 2002 09:05:06 +0200

In Germany a third option to authorize an OCSP responder is deployed in the
law-conformant PKI: a CA can authorize a key for an OCSP responder for
another CA if it issues itself an certificate to that other CAs key. This
option is used for all CAs except root which authorize its own responder
key. Thus an OCSP service of a law-compliant CA (except root) can continue
to issue reliable responses even after key compromise and revocation of its
associated CA.

This is not the same as the "local configuration", as the CA can name its
authorized OCSP responder in its own certificate.

---

From: [email-masked] (Peter Gutmann)
Date: Sat, 18 May 2002 17:29:31 +1200 (NZST)

[email-masked] writes:
>law-conformant PKI: a CA can authorize a key for an OCSP responder for another
>CA if it issues itself an certificate to that other CAs key.

Just to make sure I'm interpreting this right, what you're saying is:

  CA2 acts as a responder for CA1 ->
    CA1 certifies the responder key for CA2

Is that correct?

Peter.