As I said several times before, to produce hash collisions. Or to calculate
rainbow tables (as a previous user theorized it) you only need the

You don't need to reproduce all possible blocks.
1. SHA256 produces a 256 bit hash
2. That means it produces a value on 256 bits, in other words a value
between 0..2^256 - 1
3. If you start counting from 0 to 2^256 and for each number calculate the
SHA256 you will get at least one hash collision (if the hash algortihm is
prefectly distributed)
4. Counting from 0 to 2^256, is nothing else but reproducing all possible
bit pattern on 32 bytes

It's not about whether one computer is capable of producing the above
hashes or not, or whether there are actually that many unique 32 byte bit
patterns in the universe.
A collision can happen.

On Wed, Jul 11, 2012 at 4:34 PM, Sašo Kiselkov <>wrote:

> On 07/11/2012 04:23 PM, wrote:
> >
> >> On Tue, 10 Jul 2012, Edward Ned Harvey wrote:
> >>>
> >>> CPU's are not getting much faster.  But IO is definitely getting
> faster.  It's best to keep ahea
> > d of that curve.
> >>
> >> It seems that per-socket CPU performance is doubling every year.
> >> That seems like faster to me.
> >
> > I think that I/O isn't getting as fast as CPU is; memory capacity and
> > bandwith and CPUs are getting faster.  I/O, not so much.
> > (Apart from the one single step from harddisk to SSD; but note that
> > I/O is limited to standard interfaces and as such it is likely be
> > helddown by requiring a new standard.
> Have you seen one of those SSDs made by FusionIO? Those things fit in a
> single PCI-e x8 slot and can easily push a sustained rate upward of
> several GB/s. Do not expect that drives are the be-all end-all to
> storage. Hybrid storage invalidated the traditional "CPU & memory fast,
> disks slow" wisdom years ago.
> Cheers,
> --
> Saso
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