Subject: RE: CDP in self signed root CA

From: "Hallam-Baker, Phillip" <[email-masked]>
Date: Thu, 5 Dec 2002 20:48:27 -0800

I would like to see reference made to the precise wording in the spec
that people believe lead to these conclusions. I would consider the lack
of very explicit directions on this point to be a bug in the spec.

A self signed CA has a signer. The fact that the signer is itself means
that the only deduction that you can draw from the certificate is that
the holder of the private key asserted the contents to be true at some
time.
 
If a CRL exists that revokes the self signed CA one should logically
infer from that that the holder of the private key asserts that the
contents are false.
 
There is a CA that signs a self signed cert, the fact that it is the
subject does not change that.
 
Say what you like about a self signed cert, a self signed CRL is the
only piece of data in the entire PKI constellation that can be
absolutely considered trustworthy regardless of your trust model. Ron
Rivest proposed self signed revocation lists as the revocation mechanism
for SDSI for that reason.

        Phill

-----Original Message-----
From: Roger Younglove [mailto:[email-masked]]
Sent: Thursday, December 05, 2002 12:01 PM
To: 'Erwan Smits'; [email-masked]
Subject: RE: CDP in self signed root CA

Erwan,
I would agree with the agreement against. There is no authority above
the root CA to issue a CRL on it's cert as it is self signed. Each layer
of CAs below the root and the EEs have a level of authority above them
to issue CRLs that creates a path to validate for the CRLs.
 
Roger Younglove, CISSP
Principal Consultant
NetWorks Group
O. 810.225.4800 ex. 2245
M. 810.599.0879
E. [email-masked]
www.networksgroup.com
 
-----Original Message-----
From: Erwan Smits [mailto:[email-masked]] 
Sent: Thursday, December 05, 2002 11:36 AM
To: [email-masked]
Subject: CDP in self signed root CA
 
We are building a certificate hierarchy with 4 (CA) layers. We want to
include a CDP extension in every CA and end user certificate. At the
moment we have a discussion about the need for a CDP extension in the
Root CA. The argument against it is that it doesn't make sense because
there is no supperior CA that can sign the CRL. The argument for a CDP
is that for performing a correct path validation the CRL for every CA
(including the Root CA) and end-user certificate should be validated.
 
I scanned through RFC 3280, but it doesn't say anything about it. Does
anybody have suggestions?
 
Greetings,
 
Erwan Smits

---

From: "Santosh Chokhani" <[email-masked]>
Date: Fri, 6 Dec 2002 10:16:21 -0500

Hi Phillip:
 
I do not know exactly what Ron Rivest said and in what context, but
verifying a self-signed certificate against a CRL whose signature is
verified using the same public key as the one in the certificate is
useless.  All it does it give you false sense of security.  Granted, if
everyone behaved, you can revoke the trust anchor this way.
 
However, most likely need to prematurely revoke a trust anchor is
because of key compromise and a self-signed CRL will not help with that
since the person who compromised your key will also issue a CRL that
does not contain the trust anchor.
 
Thus, from security viewpoint, this gyration is useless.
 
Now, to the practical aspects of X.509 and PKIX.  I think the folks who
helped architect X.509 and PKIX have a lot of security savvy and they
see that there is not cryptographic security to the self-signed trust
anchors (as illustrated above).  That is why both X.509 and 3280 DO NOT
process self-signed certificate in the certification path.  It primes
the pump for the path validation engine by providing the following:
trust anchor DN, trust anchor digital signature algorithm OID, trust
anchor public key, and public key parameters (if required).  That is
all.  The rest of the checks a RP client does on the trust anchors is
all for the birds.
-----Original Message-----
From: [email-masked] [mailto:[email-masked]]
On Behalf Of Hallam-Baker, Phillip
Sent: Thursday, December 05, 2002 11:48 PM
To: [email-masked]
Subject: RE: CDP in self signed root CA

 

        Phill

-----Original Message-----
From: Roger Younglove [mailto:[email-masked]]
Sent: Thursday, December 05, 2002 12:01 PM
To: 'Erwan Smits'; [email-masked]
Subject: RE: CDP in self signed root CA

Erwan,
 
Roger Younglove, CISSP
Principal Consultant
NetWorks Group
O. 810.225.4800 ex. 2245
M. 810.599.0879
 
-----Original Message-----
From: Erwan Smits [mailto:[email-masked]] 
Sent: Thursday, December 05, 2002 11:36 AM
To: [email-masked]
Subject: CDP in self signed root CA

 
Greetings,
 
Erwan Smits