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Last Call Review of draft-jivsov-openpgp-ecc-

Request Review of draft-jivsov-openpgp-ecc
Requested revision No specific revision (document currently at 14)
Type Last Call Review
Team Security Area Directorate (secdir)
Deadline 2012-04-10
Requested 2012-03-16
Authors Andrey Jivsov
I-D last updated 2012-04-11
Completed reviews Genart Last Call review of -?? by Christer Holmberg
Secdir Last Call review of -?? by Brian Weis
Assignment Reviewer Brian Weis
State Completed
Request Last Call review on draft-jivsov-openpgp-ecc by Security Area Directorate Assigned
Completed 2012-04-11
I have reviewed this document as part of the security directorate's ongoing
effort to review all IETF documents being processed by the IESG. These comments
were written primarily for the benefit of the security area directors. Document
editors and WG chairs should treat these comments just like any other last call

This document adds support for the use of ECC as an authentication method to
OpenPGP. Two public key algorithms are supported: ECDSA and ECDH. The document
describes the supported ECC curves, how the public key is represented in
OpenPGP, and encodings for public and private keys. For ECDH, it also specifies
the KDF for creating a KEK from from ECDH shared secret and the method for key
wrapping a session key that is used to protect data traffic. This seems to be
standard OpenPGP practice for DH public key algorithms. A stated goal is to
conform to Suite B; as far as I can tell this is achieved.

I have the following comments/questions.

Section 5: A reference to ECDSA is given for both RFC 6090 and [SEC1]. The
definition in RFC 6090 supersedes [SEC1], and it is preferable to reference
just the RFC. I suggest removing "and in [SEC1]".

Section 6: RFC 6090 uses the notation "(@,@)" for the point at infinity ("point
O"), which would be better to use. This seems to be the only term in this
section specific to [SEC1], so making this change should enable you to change
your reference to RFC 6090 here too.

Section 6: The reasoning for passing the point at infinity isn't clearly
defined. Can you explain when this would be done?

Section 7: The use of "P" for parameters is confusing, since P was just used in
Section 6 to mean "Point". It would be helpful if it were "Params" or something
other name.

Section 7: It would be helpful to the reader to explain that setting ZB to "x"
is using the "compact output" of the shared secret (see RFC 6090 Section 4.2).

Section 8: Are the "5 variable-length and fixed-length fields" meant to be
OtherInfo as defined in SP800-56A? If so, mentioning this would make it easier
on the reader.

Section 8: This says "The key wrapping method is based on [RFC3394]". I hope is
it actually "conforming to [RFC3394]", which would be a clearer statement. Is
that so? If not, why?

Section 8: This section gives an example of encoding a 32-octet ASE-256 session
key into 40 octets, which seems to be the input to the key wrap. My
understanding of the AES key wrap defined in RFC 3394 is that the key input
should be just 32 octets, where it is prepended with an 8 octet IV. This
doesn't match your example though. Can this be made to match the inputs in the
RFC? For example, see the example in Section 4.6 of RFC 3394. (This would also
remove the need for padding an AES-256 key, and reduce the padding for the two
smaller sizes.)

Section 10: The statement "No changes in the format are needed for ECDSA" seems
true, but isn't it necessary to describe the Algorithm Specific Fields for
ECDSA? Is this actually defined in Section 9?

Section 13: The table of equivalent algorithm strengths seems to match claims
in SP800-57-Part1-Rev3-May2011. It would be helpful to reference this document
here as a source for the information.