Telechat Review of draft-ietf-kitten-aes-cts-hmac-sha2-10
review-ietf-kitten-aes-cts-hmac-sha2-10-genart-telechat-gurbani-2016-10-28-00

I am the assigned Gen-ART reviewer for this draft. For background on
Gen-ART, please see the FAQ at
<

http://wiki.tools.ietf.org/area/gen/trac/wiki/GenArtfaq>.

Please resolve these comments along with any other Last Call comments
you may receive.

Document: draft-ietf-kitten-aes-cts-hmac-sha2-10
Reviewer: Vijay K. Gurbani
Review Date: Jul-29-2016
IETF LC End Date: Jul-20-2016
IESG Telechat date: Unknown

This document is ready as an Informational.

Major: 0
Minor: 2
Nits: 1

Minor:
- S3, top of page 4, while defining "context": What is the format of this
optional string: is it comma separated?  Or does it not matter because the
byte-string in context is supposed to be an opaque label?  I ask because the


byte-string can contain multiple values (identities of parties, nonce, 


etc.);



consequently, how does a receiver know where one value ended and another one
began.



I realize that when "context" is used for key derivation in the KDF, 


individual


elements of the "context" does not matter; but since the text makes the 


point


that "context" may include "identities of parties who are deriving 


and/or using


the derived key material...", it seems appropriate that the recipient 


know what



separates the ID from the nonce.



- S3, middle of page 4: "When the encryption type is 


aes128-cts-hmac-sha256-128,



k must be no  greater than 256." 256 what?  Bits (I believe).  Similarly for
384.  Better to be complete.

Nits:


- S1, second paragraph: "...but do not use the simplified profile."  Any 


insight



into why simplified profile is not used may be helpful to the reader for the


sake of completeness.  (Of course, if the reasons that the simplified 


profile is


not being used are blatantly obvious to practicioners in this field, 


then don't



worry about this comment.  But if not, it may help.)

Thanks,

- vijay
--
Vijay K. Gurbani, Bell Laboratories, Nokia Networks
1960 Lucent Lane, Rm. 9C-533, Naperville, Illinois 60563 (USA)
Email: vkg@{bell-labs.com,acm.org} / vijay.gurbani at nokia.com
Web: 

http://ect.bell-labs.com/who/vkg/

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