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Re: Comments on pem-mime-07.txt

1995-01-25 14:56:00
        Number:    1
        Type:      Major Editorial
        Location:  Page 2, end of paragraph 1 in section 1.
        Comment:   The specification claims that only mechanisms are
                   changed when in fact the trust models and naming
                   conventions of PEM have been modified.
        Change:    Replace last two sentences (Page 2, end of paragraph 1)
                   with: "These changes represent a departure in
                   mechanism, trust model, and naming conventions.
                   These changes are detailed in Section 8.

They weren't modified Paul, they were set aside as a separate and
independent topic.  In other words, when you say PEM, you mean RFC 1421
and RFC 1422.  When I say PEM, I don't mean RFC 1422 and neither does
any of the PEM/MIME specification, by explicit design.

Thus, I don't believe there is any change.

        Number:    2
        Type:      Major Technical
        Location:  Page 3, paragraph 3
        Comment: It is claimed that a key pair is uniquely identified by
                   a name form and key selector combination.  This is
                   not true.  Nothing prevents a name form and key
                   selector from being used by more than one issuing
                   system (user or third party).
        Change: Provide mechanisms and recommendations for name form and
                   key selector usage to prevent multiple name form/key
                   selector pairs.  Provide a mechanism and/or
                   recommendations to uniquely associate a specific
                   certification chain with a PEM-MIME signature.
                   Change text (page 3) to reflect limitations of key
                   pair binding.

It is true that a key pair is uniquely identified by a name form and a
key selector as long as both the name form and key selector are unique.
The next revision (in the works) of the document does specify the
required characteristics of a key selector.  I will add some text
indicating that the name form must also be unique.  (Although, I should
point out that for both distinguished name and email addresses the
necessary property is already present.)

I consider this a minor editorial change.

        Number:    3
        Type:      Major Technical
        Location:  Page 3
        Comment: The PEM-MIME specification bases security primarily on
                   public/private key pairs.  This is a problem when the
                   identity of an entity depends not only on the key
                   pair, but also the context of the key certification
                   (whether old PEM model or newer PGP like models).
        Change: Provide text giving recommendations for use of new name
                   forms.  Provide a mechanism to uniquely associate a
                   specific certification chain with a PEM-MIME
                   signature applied to data.

I don't understand.  A name form is used to associate a human consumable
label to a key.  A user owning a key gets to choose this and assert it
to all those with whom the user communicates.  The protocol doesn't care
what the value is.  What kind of recommendations are you looking for?

As for the certification chain, the topic is explicitly excluded from
the scope of the document.

I don't know the type of this change since I don't understand it.

        Number:    4
        Type:      Major Editorial
        Location:  Throughout
        Comment: The PEM-MIME (version 7) specification documents five
                   ways to identify public keys (E-mail Addresses,
                   Arbitrary Strings, Distinguished Name, raw Public Key
                   and Issuer Distinguished Names).  The description of
                   these mechanisms focus on the means to retrieve a
                   public keys.  Digital signatures provide a senders
                   identifty based on the public/private key pair and
                   the context in which the keys might be certified.
                   The specification does not indicate when and how a
                   "identifier" can be unabibuosly mapped to a single
                   certification chain.  The specification needs to
                   describe when this lack of mapping is a feature and
                   when it is a flaw.
        Change: Add text to describe the usage and limitations of the
                   five identifiers.  Provide recomendations for the
                   usage of each name form (e.g. when is a PK prefered
                   to a EN).

Your comment is confusing name forms (there are 3) with identifiers
(there are 5).  We explicitly do not provide guidance to a user as to
which name form or which identifier to use.  The intent is that a user
may choose whichever form suits their fancy or is best suited to the
environment in which it will be used.

I'm not aware of any inherent limitations implicit in the use of any
particular name form or identifier.  Some provide more information for
implementations and thus an implementation may be able to be more
helpful when they're present, but I wouldn't consider this a limitation.

I don't believe there is any change.

        Number:    5
        Type:      
        Location:  Page 17
        Comment:   The text below is far to fuzzy about the new PEM-MIME 
                   certificate formats:
        >    NOTE: Insofar as a certificate represents a mechanism by which a
        >    third party vouches for the binding between a name and a public
        >    key, the signing of an application/pemkey-data body part is a
        >    similar mechanism.
        Change: Include specific recomendations for the use of signed
                   application/pemkey-data body parts.  Provide examples
                   of signed application/pemkey-data body parts.

The next version of the document has a specific recommendation about how
one might use application/pemkey-data.  I don't remember offhand about
the examples but I'll look and make sure there is one.

I consider this a minor editorial change.

        Number:    6
        Type:      Major Editorial
        Location:  Throughout
        Comment: The RFC1422 hierarchies are still supported in the
                   specification, but no guidelines are provided for
                   resolving what happens when the "top down" 1422
                   hierarchy meets the "roll your own" PEM-MIME
                   certificate-like structures.  No guidelines are
                   provided for the interworking of the various name
                   forms.
        Change: Provide recommendations for interworking of 1422
                   certificates with the new name forms and raw public
                   key approaches.

This topic is explicitly excluded from the scope of the specification.

Thus, there is no change.

        Number:    7
        Type:      Major Editorial
        Location:  Page 32
        Comment: The references a specification that it claims to
                   replace (RFC1421).
        Change: Text from RFC1421 should be borrowed and placed in the
                   PEM-MIME document.  The grammar should be placed in
                   section 9.

We are, in fact, doing this now.

This is a major editorial change.

        Number:    8
        Type:      Minor Editorial
        Location:  Section 9 and Page 32 (Appendix: Imported Grammar)
        Comment: Separating the imported grammar from the collected
                   grammar makes the specification more difficult to
                   read.
        Change:    Move the text in Section 14 to Section 9.

The problem is we want to explicitly observe for the reader that the
correct grammar only exists in its original form, not in the borrowed
form in this document.

I'll see if there's a better way to organize it.

        Number:    9
        Type:      Minor Editorial
        Location:  Section 3.1
        Comment: The specification does not address the issues of "white
                   space" and digital signatures.
        Change: Add text that describes white space issues in a
                   digitally signed Suggestion - include an example
                   describing the scanning of signed documents that have
                   trailing white space.

This is handled by MIME.  There is nothing for PEM todo.

Jim

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