Subject: [dnsext] question on "SHA-2"

From: Edward Lewis <[email-masked]>
Date: Wed, 14 Jan 2009 10:28:08 -0500

Referring to http://tools.ietf.org/id/draft-ietf-dnsext-dnssec-rsasha256-10.txt

In recent weeks I have seen buzzword articles talking about "SHA-2" 
and "SHA-256" and began to wonder if the two are one in the same. 
According to this passage early in the draft:

#   To refer to both SHA-256 and SHA-512, this document will use the name
#   SHA-2.  This is done to improve readability.  When a part of text is

(I was originally going to ask: What's the difference between SHA-256 
and SHA-2 and please don't say "56?")

I wondered how commom place this is because I'm against making DNS or 
DNSSEC-centric definitions that conflict with the outside world. 
Looking up in Wikipedia:

# The SHA-2 family uses an identical algorithm with a variable key size
# which is distinguished as SHA-224, SHA-256, SHA-384, and SHA-512.

I'd be more comfortable if we complied with that terminology, and 
then said "but DNS we don't do 224 or 384.  I'd also like there to be 
some more fluff describing the naming convention of the SHA-s, or, 
just a reference to the naming convention (I don't suppose we can use 
Wiki URLs).
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Edward Lewis             
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From: Scott Rose <[email-masked]>
Date: Wed, 14 Jan 2009 11:06:17 -0500

Edward Lewis wrote:
> Referring to
> http://tools.ietf.org/id/draft-ietf-dnsext-dnssec-rsasha256-10.txt
> 
> In recent weeks I have seen buzzword articles talking about "SHA-2" and
> "SHA-256" and began to wonder if the two are one in the same. According
> to this passage early in the draft:
> 

254 actually.  :)

> DNSSEC-centric definitions that conflict with the outside world. Looking
> up in Wikipedia:
> 

That is the commonly understood definition, but SHA-2 hasn't been
"officially" defined that way (FIPS-180 doesn't use the term SHA-2 for
example), just that those hash functions have been lumped together under
a common umbrella term.  It's sometimes referred to as the "SHA-2
family" in some NIST comments:
http://csrc.nist.gov/groups/ST/hash/statement.html

Scott

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Scott Rose            Computer Scientist
NIST
ph: +1 301-975-8439
[email-masked]

http://www-x.antd.nist.gov/dnssec
http://www.dnsops.gov/
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From: Edward Lewis <[email-masked]>
Date: Wed, 14 Jan 2009 11:44:25 -0500

>254 actually.  :)

Funny.  Ha.

>http://csrc.nist.gov/groups/ST/hash/statement.html

I know my comment is an annoying nit, but in the spirit of still 
trying to explain that "TSIG" neither covers a transaction nor is a 
signature (related to the misnaming of that mechanism which wasn't 
caught until the Security Area AD voiced a mild objection[1]), and in 
the more general rule of not defining non-DNS terms, my suggestion is 
that the document include what Scott typed here.  And include any 
reference-able documents to show that the terminology is "not 
invented here."

[1] I wasn't ringside for that, but, if he didn't raise a mild 
objection, I doubt the name would have stuck.  I believe it was 
Stephen Kent who objected - he was once an AD and may or may not have 
been the sitting one at the time.  My memory is hazy on this - maybe 
someone ringside can fill in.  If there's any truth to my hazy memory.
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Edward Lewis
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From: Scott Rose <[email-masked]>
Date: Wed, 14 Jan 2009 11:53:00 -0500

Edward Lewis wrote:
> I know my comment is an annoying nit, but in the spirit of still trying
> to explain that "TSIG" neither covers a transaction nor is a signature
> (related to the misnaming of that mechanism which wasn't caught until
> the Security Area AD voiced a mild objection[1]), and in the more
> general rule of not defining non-DNS terms, my suggestion is that the
> document include what Scott typed here.  And include any reference-able
> documents to show that the terminology is "not invented here."
> 

Sounds like a good idea - given that not everyone may know that SHA-2 is
just a general term and covers more than SHA-256/512.

Scott

> objection, I doubt the name would have stuck.  I believe it was Stephen
> Kent who objected - he was once an AD and may or may not have been the
> sitting one at the time.  My memory is hazy on this - maybe someone
> ringside can fill in.  If there's any truth to my hazy memory.

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From: Jelte Jansen <[email-masked]>
Date: Wed, 14 Jan 2009 18:11:14 +0100

>> At 11:06 -0500 1/14/09, Scott Rose wrote:

well, technically, if a sha-1 digest is 160 bits, and a sha-256 digest is 256,
then the difference would be -64. As for -224, -384 and -512... ok i'll stop now

> just a general term and covers more than SHA-256/512.

Ok, if nobody objects, i'll add your text (perhaps slightly modified) to the
next final draft. Now quit bringing up stuff ;)

Jelte