full-disclosure - Re: Chinese Professor Cracks Fifth Data Security Algorithm (SHA-1)

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Message-ID: <4601A273.4050807@thievco.com>
Date: Wed, 21 Mar 2007 14:24:03 -0700
From: Blue Boar <BlueBoar@...evco.com>
To: 3APA3A <3APA3A@...URITY.NNOV.RU>
Cc: full-disclosure <full-disclosure@...ts.grok.org.uk>,
	Secure Coding <SC-L@...urecoding.org>
Subject: Re: Chinese Professor Cracks Fifth Data Security
 Algorithm (SHA-1)

My understanding that the kind of birthday attack under discussion would
start at 80-bits if SHA-1 (at 160-bits) were 100% secure. The attack
under discussion is reported to reduce that to the neighborhood of
60-something bits.

I am not a mathematician though, so I would be perfectly willing to
believe I was wrong about that.

					BB

3APA3A wrote:
> Dear Blue Boar,
> 
> It's  not  clear  if  this 'crack' cam be applied to birthday attack. My
> in-mind computations were: because birthday attack requires ~square root
> of N computations where bruteforce requires ~N/2, impact of 2000 times N
> decrease  for birthday is ~64 times faster. 64 = 2^6. Because complexity
> is ~square root of possible combinations, it's equivalent of traditional
> birthday  attack,  with  160-(2*6)=148  bits  hash (150 is my mistake in
> in-mind computations).
> 
> Of  cause,  since  I  completely  wasted 10 years after obtaining Master
> degree  in  Mathematics  and  3 years after loosing last pencil I may be
> completely wrong in computations :)
> 
> --Wednesday, March 21, 2007, 9:48:55 PM, you wrote to 3APA3A@...URITY.NNOV.RU:
> 
> BB> 3APA3A wrote:
>>> I  know  meaning  of  'hash  function'  term,  I  wrote  few articles on
>>> challenge-response   authentication   and   I  did  few  hash  functions
>>> implementations  for  hashtables  and  authentication  in FreeRADIUS and
>>> 3proxy.  Can  I  claim  my  right  for  sarcasm after calling ability to
>>> bruteforce 160-bit hash 2000 times faster 'a crack'?
> 
> BB> Fair enough, your sarcasm tags didn't render properly in my MUA. I was
> BB> fooled by you stating that the birthday attack would be 150 bits.
> 
> BB> 						BB
> 
> 

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