Subject: Re: [Emu] WG Last Call: draft-ietf-emu-eap-gpsk-03.txt

From: "M. Vanderveen" <[email-masked]>
Date: Thu, 8 Feb 2007 15:10:32 -0800 (PST)

I have reviewed the draft and found no problems.
Michaela

----- Original Message ----
From: Joseph Salowey (jsalowey) <[email-masked]>
To: [email-masked]
Sent: Wednesday, February 7, 2007 7:52:10 PM
Subject: [Emu] WG Last Call: draft-ietf-emu-eap-gpsk-03.txt

This is a working group last call for draft-ietf-emu-eap-gpsk-03. 

Send your comments to the EMU list by March 7, 2007.  Please respond to
this call even if you have reviewed the draft and found no problems.  

The document can be accessed here:
http://www.ietf.org/internet-drafts/draft-ietf-emu-eap-gpsk-03.txt

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From: "Bernard Aboba" <[email-masked]>
Date: Fri, 09 Feb 2007 06:23:20 -0800

Review of draft-ietf-emu-eap-gpsk-03.txt

Section 1

"   At present, several pre-shared key EAP methods are specified, most
   notably

   o  EAP-PAX [RFC4746]
   o  EAP-PSK [I-D.bersani-eap-psk]
   o  EAP-TLS-PSK [I-D.otto-emu-eap-tls-psk] and
   o  EAP-SAKE [I-D.vanderveen-eap-sake].

   Each method has its particular benefits but also its particular
   deficiencies.  EAP-GPSK is a new EAP method that tries to combine the
   most valuable characteristics of each of these methods and therefore
   attempts to address a broad range of usage scenarios."

I would delete this discussion since it doesn't really relate to the
design goals of EAP-GPSK.  As it stands, this statement is too vague
to motivate the design, and discussion of "deficiencies" without
providing justification is problematic.

"      EAP-GPSK should be easy to implement and therefore quickly
      available."

I would leave out "and therefore quickly available".  You might also
provide some more info on what makes a method easy to implement,
such as single purpose (PSK), use of commonly available algorithms,
etc.

"   Wide applicability:

      EAP-GPSK has been designed in a threat model where the attacker
      has full control over the communication channel.  This is the EAP
      threat model that is presented in Section 7.1 of [RFC3748]."

I think a more appropriate title would be "Security model".

Efficiency

You might mention round-trips here.

This section should also mention that Privacy is not supported.

Section 4

In addition to the Method-Id, this section should define the Peer-Id
(ID_Client), Server-Id (ID-Server) and Session-Id
(Type-Code || MID).

Section 5

SHA-1 is on a path to deprecation by NIST, so I am concerned about
including this algorithm.

The KDFs do not appear to comply with the NIST KDF recommendation included 
in this draft:
http://www.watersprings.org/pub/id/draft-dang-nistkdf-01.txt

Or am I not reading it correctly?