Subject: Re: I-D ACTION:draft-ietf-smime-escertid-01.txt

From: "Denis Pinkas" <[email-masked]>
Date: Wed, 3 May 2006 15:54:58 +0100

I have several problems with draft-ietf-smime-escertid-01.txt.

In RFC 2634, we have section "5.4 called Signing Certificate Attribute Definition"

The proposal is to add a section 5.4.1 to define the v2 version first (!) 
and then the current version (with SHA-1). This should be done in the reverse way:

 - first a section 5.4.1 to define the current version (with SHA-1),
 - then a section 5.4.2 to define the v2 version.

After this restructuring, I have some problems with the text itself :

Issue 1 (page 4):

   "Applications SHOULD recognize both attributes as long as
   they consider SHA-1 to be sufficiently descriminating".

"descriminating" is not crystal clear for me. Would it be possible 
to have the same idea expressed using a different wording ?

Issue 2 (pages 4 & 5):

There is a duplication of the same paragraph (one is enough):

   "The signing certificate attribute is designed to prevent the simple
   substitution and re-issue attacks, and to allow for a restricted set
   of authorization certificates to be used in verifying a signature".

Issue 3 (page 7):

   "The issuer/serial number pair would therefore normally be sufficient 
   to identify the correct signing certificate.  (This assumes the same 
   issuer name is not re-used from the set of trust anchors.)"

The assumption between the parenthesis is insufficient to correctly identify 
the correct signing certificate. The sentence needs to be changed.

Issue 4 (page 7):

   "In the cases
   where the issuer/serial number pair is not used in the sid or the
   issuer/serial number need to be signed, they should be placed in the
   issuerSerial field of the ESSCertIDv2 structure."

The issuer/serial number pair can be used in the sid, but since it is unsigned, 
it is insufficient to correctly identify the correct signing certificate. 
So this rational is incorrect. The sentence needs to be changed.

Finally, I would propose that the next draft proposes a global replacement 
for section 5.4 to make sure that the whole section is consistent 
(and that the text in it is not redondant).

Denis

>A New Internet-Draft is available from the on-line Internet-Drafts directories.
>This draft is a work item of the S/MIME Mail Security Working Group of the IETF.
>
>	Title		: ESS Update: Adding CertID Algorithm Agility
>	Author(s)	: J. Schaad
>	Filename	: draft-ietf-smime-escertid-01.txt
>	Pages		: 18
>	Date		: 2006-4-18
>	
>In the original Enhanced Security Services for S/MIME draft, a
>structure for cryptographically linking the certificate to be used in
>validation with the signature was introduced, this structure was
>hardwired to use SHA-1.  This document allows for the structure to
>have algorithm agility and defines new attributes to deal with the
>updating.
>
>A URL for this Internet-Draft is:
>http://www.ietf.org/internet-drafts/draft-ietf-smime-escertid-01.txt
>
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Regards,

Denis Pinkas