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

2006-08-24 12:26:29


In order to solve my two concerns, the faster is to propose a text replacement.
I hope this will clarify my statements.

The statement in the parenthesis is not true. The issuer/serial number is not sufficient.

I propose the following as a global replacement:

  The issuer/serial number pair is the method of identification of
  certificates used in [PKIXCERT].  The issuer/serial number pair may
  be insufficient since two or more CAs with the same DN could exist in
  in different branches from a given certification tree.  The
  issuer/serial number pair may be used as a hint to fetch the
  certificate(s).  The issuer/serial number pair can be stored in the
  sid field of the SignerInfo object.  In the cases where the
  issuer/serial number pair is not used in the sid, it should be
  placed in the issuerSerial field of the ESSCertIDv2 structure.
  In some cases, hashes are used by certificate stores as a method of
  indexing and retrieving certificates, hence another reason for
  having the issuer/serial number pair optional.

  The hash of the entire certificate allows for a verifier to check
  that the certificate used in the verification process is indeed the
  one the signer intended to be used.  The use of the hash is
  required by this structure since the detection of substituted
  certificates with the same DN and serial number is based on the
  fact they would map to different hash values.


 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.

I prefer the existing ordering.  I would rather have the items that people
are to be using occur first and then obsolete items rather than the other
way around.  I have not changed this.

 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".

I believe that not having any descriptive text at these locations and
jumping directly into the ASN.1 to be a poor choice.  I have not changed

 Issue 3 (page 7):

   "The issuer/serial number pair would therefore normally be
   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.

I do not understand your statement.  If the statement in parenthesis is
true, then it is sufficent.  If the statement in the parenthesis is not
true, then issuer/serial number is not sufficent.  Please re-read the text
and explain better what your problem is.

 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.

I have no idea what you are trying to state here.  My sentence and your
comment do not seem to be coming from the same context.  Please re-read the

 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).

I can understand your concern, however I believe that the current layout is
better and more explicit for the RFC editor.



 >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
 >A URL for this Internet-Draft is:
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 Denis Pinkas

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