[Cryptography] Google announces practical SHA-1 collision attack

[Theodore Ts'o]

On Sun, Feb 26, 2017 at 09:04:45PM -0600, Nikita Borisov wrote:
> On Sat, Feb 25, 2017 at 5:06 PM, Peter Gutmann <pgut001 at cs.auckland.ac.nz>
> wrote:
> 
> > They announced an attack that requires a nation-state's worth of resources
> > and
> >
> 
> The cost estimates were around $500K at normal EC2 prices and $100K at spot
> prices. I'd have imagined that nation states command rather more resources
> than that!

If I'm not mistaken, those are the costs for the *second* phase of the
attack (110 GPU years).  However, you have to first carry out the
*first* phase of the attack, which takes 6200 CPU years.

Aside from throwing out numbers which are much scarier, which make for
good headlines and scaring clients to score more consulting time, is
there a reason why people are fixated on the 110 GPU year "second
phase" number, and not the 6200 GPU years "first phase" number?

						- Ted