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Re: [STDS-802-11-TGAI] Contribution uploaded & MDR open issues (and AEAD/GCM clarifications)


  Hello,

On 5/12/15 9:35 AM, "Jouni Malinen" <j@xxxxx> wrote:

On 11 May 2015, at 6:51 am, Fangping (Device Standard) <ping.fang@xxxxxxxxxx> wrote:
For MDR, there are two open comments.
b) P128L28 the little-endianness of 802.11 disagrees with 'first bit is 1'
Editor[M] Dangerous as specified - should be described as an integer field of 13 octets width. The special value should be 2**((13*8)-1). This comment shall be resolved in IEEE802.11 May meeting.
Input is needed to close the comment. Please let me know if you would like to work on this.

I posted an initial version of proposed changes to AEAD/GCM design to address both this comment and CID 7416 as discussed yesterday. I'm planning on bringing this up in AM2 today for discussion. Please note that there are changes in the design compared to what was described yesterday, so we'll need to discuss this in the TG to see if there is consensus on the somewhat different approach.

The document is here:

  It appears that the modifications to 11.11.2.4.3 are for a different version of the draft.
Version 4.3 does not contain the paragraph that is being modified; it has something very
similar but it's not the same. Also, why set both AEAD counters to zero when the PTKSA is
created and then construct the nonce in the way specified in 11.11.2.6? Why not just set
the AEAD counters to be all zeros on one side and 0x01 || rest zeros on the other (or better
0x80 || rest zeros) at PTKSA creation time and then just increment when used? 

  Also I have a slight preference to making the encrypted data in the (Re)Association
frames to be the tag concatenated with cipher text instead of the cipher text
concatenated with the tag. The reason is:

   t = p
   c = p + taglen

seems better to me than:

  c = p
  t = p + len(p) - taglen

but that's not a hill I'm willing to die on so if the author likes it better C || T then I
won't complain. 

  regards,

  Dan.

- Jouni

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