Subject: [OPSAWG] Kathleen Moriarty's Yes on draft-ietf-opsawg-hmac-sha-2-usm-snmp-06: (with COMMENT)

From: "Kathleen Moriarty" <[email-masked]>
Date: Tue, 12 May 2015 12:27:43 -0700

Kathleen Moriarty has entered the following ballot position for
draft-ietf-opsawg-hmac-sha-2-usm-snmp-06: Yes

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COMMENT:
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Thanks for your work on this draft!  It's great to see the improvements
in security.

This is just a comment and not critical at all… I found this sentence at
the bottom of the second bullet of 4.1 a little odd:
      as opposed to the truncation to 12 octets in HMAC-MD5-96 and HMAC-
      SHA-96.

Since the guideline is to truncate the size in half and have 80 or more
bits for a HMAC, you are covered and already cite the appropriate RFCs. 
Is this there just for history of previous solutions?  Or would it be
better to just state the guidance so folks understand why you chose the
truncation size?  You can do nothing with my comment, it's just a
question as the text had me curious.  And I see that you have included
the HMAC truncation guidance in the security considerations section
already.

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From: t.petch <[email-masked]>
Date: Thu, 14 May 2015 14:27:43 +0100

----- Original Message -----
From: "Kathleen Moriarty" <[email-masked]>
Sent: Tuesday, May 12, 2015 8:27 PM

Kathleen

I am puzzled.  That section, 4.1, is entitled
"Deviations from the HMAC-SHA-96 Authentication Protocol"
(and HMAC-MD5-96 is then added in the first paragraph).   It goes on to
say
"Precisely, they differ from the HMAC-MD5-96 and HMAC-
   SHA-96 authentication protocols in the following aspects:
"
so omitting that last sentence would seem, IMHO, to weaken that
'precisely'.

As you say, the Security Considerations do do a good job of covering the
idea of truncation in general.

So I think that that sentence you comment on has a place in the I-D..

Tom Petch