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Liaison Statement: Response to Liaison Statement on ITU-T Recommendation X.1034

Submission Date: 2008-09-11
From: IETF EMU WG (Joseph Salowey)
To: ITU-T SG 17 (tsbsg17@itu.int, zeltsan@alcatel-lucent.com)
Cc:emu-chairs@tools.ietf.org
emu@ietf.org
emu-ads@ietf.org
sob@harvard.edu
Response Contact: emu@ietf.org
emu-chairs@tools.ietf.org
emu-ads@tools.ietf.org
Technical Contact: emu-chairs@tools.ietf.org
Purpose: In response
Attachments: (none)
Body:
The EAP Method update (EMU) working group in the IETF has reviewed the
document "ITU-T Recommendation X.1034" that is the subject of a liaison
statement submitted on 2008-08-06. Does the ITU-T have further plans in
this area, such as more EAP method analysis or definition?  If so,
perhaps more coordination between the IETF and the ITU-T in this area
is needed.  The members of EMU WG provided the following comments,
which we hope are useful in finalizing the contents of X.1034.

A. Comments on section 3.2

1. It is not clear if the definition of PFS aligns with the definition
in other documents such as from the "Handbook of applied cryptography"
(http://www.cacr.math.uwaterloo.ca/hac/about/chap12.pdf).

2. The server compromised-based attack appears not to be an attack, but
rather a way to mitigate the server compromised attack.  These
definitions are not clear. 

B. Comments on section 6.1

1. In figure 1 - Replace TDP with TCP, SCP with SCTP and "UDP or IP"
with "UDP over IP" 
2. Throughout the document replace DIAMETER with Diameter.
3. The following sentence is misleading: "the authenticator exchanges
random numbers with the supplicant to obtain a fresh cryptographic key;
thus resulting in perfect forward secrecy." Fresh keys are not
sufficient to fulfill the criteria for PFS. 

C. Comments on section 7.2 and 7.5

1. The "Prevention of domino effect or Denning Sacco attack" is a
property of the system and not specific to the EAP method.  
2. Authorization is not communicated in EAP.  It is communicated from
the Authentication server to the authenticator based on the identity
authenticated by EAP.  
3. The requirement for "Protection against server compromised
dictionary attack" is not clear.  If encrypted storage is all that is
necessary then why is this a property of a protocol and not just a
specific implementation detail?  
4. Section 7.5 states that the appendix can be used to select from many
existing EAP methods, however section I only analyzes a small subset of
EAP methods. 

D. Comments on table I-1:

General: EAP-MD5 and EAP-SRP are not widely deployed.  This section
claims to analyze "well-known" EAP methods, however it only analyzes
two of the many methods that are deployed.  There are EAP methods that
provide additional properties but they are not listed in the table.
There are more detailed investigations available, such as
http://www-public.tu-bs.de:8080/~y0013790/thesis-otto-eapmethods.pdf. 

1. EAP-SRP 

i.	EAP-SRP is not defined in RFC 2945.  There is no current
documentation for an EAP-SRP (There was a draft that expired many years
ago).  It is not clear what this evaluation was done against.   


2. EAP-MD5 

i.	EAP-MD5 does not provide mutual authentication or resistance to
dictionary attacks 
ii.	EAP-MD5 does not provide protection from dictionary attacks. 
EAP-MD5 can be used with passwords.
iii.	In general EAP-MD5 is not very useful since it does not generate
session keys. It would be more appropriate to include EAP-GPSK. 

4. EAP-TLS 

i.	EAP-TLS Can provide user identity privacy (RFC 5216, section 2.1.4)

ii.	EAP-TLS provides fragmentation support 
iii.	EAP-TLS does not use passwords and hence it is more appropriate to
say that password-based issues are not applicable.
iv.	RFC 5216 provides unique naming for keys and sessions for EAP-TLS

5. EAP-AKA 

i.	EAP-AKA provides support for user privacy 
ii.	EAP-AKA does not use passwords and hence it is more appropriate to
say that this issue is not applicable.
iii.	RFC 5247 provides unique naming for keys and sessions in EAP-AKA

E. Comments on Bibliography

1. RFC-2716 is obsolete, EAP-TLS is defined in RFC 5216 
2. draft-ietf-eapkeying-21.txt has been published as RFC 5247