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Re: [STDS-802-11] document 11-14/1104r1 for TGmc



--- This message came from the IEEE 802.11 Working Group Reflector ---
All,

TGmc has one timeslot left this week, and discussion of these
items is not on the agenda at this point. Given that the agenda is already very full,
we will not get to these comments this week.

I'll schedule discussion of CIDs 3439 and 3432 for an upcoming teleconference.

Thanks,

Dorothy





On Thu, Sep 18, 2014 at 1:01 AM, Jon Rosdahl <jrosdahl@xxxxxxxx> wrote:
--- This message came from the IEEE 802.11 Working Group Reflector ---
Hi Dan,
   As doc 11-14/1104r1 has a lot of CIDs, it took a bit of reading to find where your concern area was in the document.  (for those reading along it is I believe CID 3432, 3426, 3427, 3429).

I am confused in reading 11-14/1104r1 on these CIDs because it does not seem consistent in the naming.
Is it supposed to be SHA1 or SHA-1 for example (as you note).

So to help those of us that do not work with the security protocols daily, what is the appropriate names...can we safely say that it is supposed to be SHA1, SHA256, SHA128.
Given the nominal names then I understand from your suggestion that the "-xxx" is then the amount to truncate to. (without the word truncate to prefix the name).

The other parts that are noted as needing to be change you do not comment on.
Do we need to say "delete securely" in all cases or is "delete" sufficient.
does "destroy" imply "delete securely" and thus it is a valid term to use, and should be used when ever we mean "delete securely"
Thanks,
Jon


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On Thu, Sep 18, 2014 at 1:14 AM, Dan Harkins <dharkins@xxxxxxxxxxxxxxxxx> wrote:
--- This message came from the IEEE 802.11 Working Group Reflector ---

  Hello,

  I may not be at the 11mc session where 11-14/1104r1 is presented so I
want to get discussion on it started on the mailing list.

  There are some issues with the proposed description of various designations
of the Secure Hash Algorithm family of hash functions. In an effort to obtain
what the author views as "consistency" he has introduced ambiguity and,
in my opinion, incorrectness.

  There are 3 families of the Secure Hash Algorithm. There's the 1st family of
SHA, (which is just designated SHA1) and there's the 2nd family of SHA (known
as SHA2) which is SHA256 and SHA512, including truncated versions of each,
SHA224 is a truncated version of SHA256 and SHA384 is a truncated version of
SHA512. The 3rd family of SHA, SHA3 is a weird beast that we don't need to
trouble  ourselves with since we're not using it.

  It is important to understand, though, that SHA1, SHA256, and SHA512 are
different. They are not just truncated versions of the same function. And while
SHA256 does actually produce 256-bits of digest output, SHA1 does not 
produce 1-bit of digest output, it produces 160-bits.  But we (802.11) do
truncate the output of SHA family hash functions. For instance, we sometimes
want only the first 128-bits of SHA1. Just to make things more complicated,
we also use the HMAC construct with a SHA family algorithm.

  So how to deal with identifying the appropriate algorithm in the appropriate
family of SHA, whether it is alone or as HMAC, and how to identify the particular
output bit length that we are concerned with? 11-14/1104r1 does a poor job.
Let me propose a better way:

  * the particular algorithm of the family is used without any hyphens— for
     example, it's SHA256 not SHA-256, and it's SHA1 always. 

  * when we want to truncate we add a hyphen and indicate the bit length we
     want to use— for example, it's SHA256-128 (not sure why we'd do this but it's
     an example) or SHA1-128. 

  * if we don't add a hyphen and number indicating truncation then the entire
     length of the algorithm output is used.

  * if we want to use the HMAC construct we prepend "HMAC-" to the SHA family
     algorithm indicated, including any possible indication of truncation— for
     example, HMAC-SHA256 or HMAC-SHA1-128. 

  * if we don't prepend "HMAC-" then we are using the algorithm directly, and
     not as a keyed hash function.

  While 11-14/1104r1 does this correct in some cases— it proposes to 
change "HMAC-SHA-256" to "HMAC-SHA256"-- it does it wrong in other
cases— it proposes to change "SHA1" to "SHA-1".

  Also, if we adopt this more correct way of referring to these various 
incarnations of hashing we do not need to say something like
"Truncate-128(HMAC-SHA1(xxx))" we just say HMAC-SHA1-128(xxx)".

  Minor grammatical gripe: there is no such algorithm called 
"HMAC-SHA1-64", or even "HMAC-SHA-1-64" so we should not be using
the definite article when describing the use of SHA1 in an HMAC 
construct while truncating the output to 64 bits.

  Please modify 11-14/1104r1 to adopt this more correct terminology
before it gets adopted.

  regards,

  Dan.



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