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Re: In case y'all didn't catch it yet...
From: Bart.Lansing () kohls com
Date: Wed, 16 Feb 2005 10:48:55 -0600


Tim <tim-security () sentinelchicken org> wrote on 02/16/2005 10:10:44 AM:

Hello,

A couple of things to note from mr schneider's blog warning...

It's "schneier", not "schneider".

Thx for the correction, eyes saw a "d", expecting it to be there based on 
commonality...isn't the mind a wonderful thing?




Fact..until it's published and the method handed out and it's 
replicated 
independently, SHA-1 is NOT broken.

I feel that statement is misleading.  SHA-1 may be broken.  It may have
been broken years ago, for all we know, by some well-funded government.
Just because the methods aren't available, that doesn't mean it isn't
broken.

Does this mean we can all trust these researchers to be telling the
truth?  No.  No matter how trustworthy we think these guys are, the
public can't be 100% sure that SHA-1 collisions can be found, until the
methods are public and tested.  That I agree with, and I think that's
probably what you meant.

Yes, what I meant, should have been stated more clearly, thx for the more 
accurate re-statement



Fact..the people posting here missed a fairly important bit of 
schneider's 
blog-post, and I quote: 

The paper isn't generally available yet. At this point I can't tell 
if 
the attack is real.

read it again:  >>AT THIS POINT I CAN'T TELL IF THE ATTACK IS REAL.

Yes, exactly.  In a way, it is all FUD until the methods are published.
Hard to ignore FUD, though.

Sadly yes...but I have higher expectations of this group of people than I 
do of John Q. Public.



Fact:  If the paper and method are sound...the sky STILL is not 
falling 
(although it will be raining pretty darned hard)...2^69 
operations...to 
get a collision...how many hours of current gen cpu cycles?? (some 
notes 
from the blog thread postulate a 4 ghz machine would need 4000 
years...4000 CPU@ 4 ghz ea ...1 year.)  Based on the rumors, would I 
entrust state secrets to SHA-1? Nope.  Digital signature on a document 

authorizing the use of Nukes against Utah?  Nope.  Failing that level 
of 
protection requirement, for the time being, of course I would, and 
will.


True, if the amount of computation required is 2**69, then it is still
an attack out of reach for most applications, since it is often cheaper
just to bribe people, or to hold them at gunpoint.

However, if a specific collision in SHA-1 is released, as it was with
MD5, then there are some special case attacks that can be done, without
needing all that computational power. See:
  http://www.doxpara.com/md5_someday.pdf

In addition, if these methods are eventually made public, peer review
may yield extensions which are more efficient.  It is at least something
to keep an eye on.

tim

I could not agree with you more, it is not only something of interest from 
the purely theoretical "oh cool, those are some very bright folks..look at 
this!" standpoint, but from the "Ok, now if this is real, how long will 
the users who rely on this really have to transition to a new PKI 
environment or some completely "other" way of handling secure 
non-repudiation/identification" standpoint as well.

Good points,

Cheers

Bart


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