On Tue, 30 Dec 2008 20:27:07 EST, [email protected] said:

> > Is this attack effective against SHA-1?  How much longer would it take?
> 
> http://www.win.tue.nl/hashclash/rogue-ca/
> 
> Read 5.3.4 for MD5:
> The total complexity of the collision construction can be estimated at 2^51.x 
MD5 compression function calls, when 30 GB of memory is available.
> 
> And the FAQ for SHA-1:
> Status of the theory: at the Rump Session of Crypto 2007 they estimated the
> complexity of their attack for collisions with identical initial IHVs to be
> 2^61 calls to the compression function. For chosen-prefix collisions they
> estimated in 2006 a complexity of just below the birthday bound of 280.
> Improvements on the latter result are probably possible, but nobody has looke
d
> into this.
> 
> So... an order of 2^10 harder.

Damn apples and oranges. 2^51 for chosen-prefix MD5, 2^61 for SHA-1 collide,
2^80 for chosen-prefix SHA1.  Do the rest of the math yourself, I'm obviously
temporarily incompetent. ;)

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