On Sat, Aug 15, 2009 at 09:12:58PM +0100, John Tapsell wrote:
> 2009/8/15 Bryan Donlan <bdonlan@xxxxxxxxx>:
> > coreutils is licensed under GPLv3, and git under GPLv2 (only), so
> > you'd need permission from all contributors to the implementation in
> > order to relicense under GPLv3. A quick grep of the history suggests
> > these contributors to be:
>
> X11 also requires a fast SHA1 implementation. It uses this to check
> if two pixmaps are the same. So it would be really nice to relicense
> under a liberal enough license that xorg can use it.
If the checksum isn't being exposed in the protocol (i.e., it's just
internal to the X server), one possibility for X11 is to consider to
use the SHA-3 candidate Skein instead. After receiving a large amount
of evaluation by cryptographic experts, it was one of the 18
algorithms (our of an original 64 entries) that have made it the 2nd
round of the NIST competition. It's also *substantially* faster than
SHA:
One exception to this is Skein, created by several well-known
cryptographers and noted pundit Bruce Schneier. It was designed
specifically to exploit all three of the Core 2 execution units
and to run at a full 64-bits. This gives it roughly four to 10
times the logic density of competing submissions.
This is what I meant by the Matrix quote above. They didn't bend
the spoon; they bent the crypto algorithm. They moved the logic
operations around in a way that wouldn't weaken the crypto, but
would strengthen its speed on the Intel Core 2.
In their paper (PDF), the authors of Skein express surprise that a
custom silicon ASIC implementation is not any faster than the
software implementation. They shouldn't be surprised. Every time
you can redefine a problem to run optimally in software, you will
reach the same speeds you get with optimized ASIC hardware. The
reason software has a reputation of being slow is because people
don't redefine the original problem.
http://www.darkreading.com/blog/archives/2008/11/bending_skein_c.html
For more information and some optimized implementation, see:
http://www.skein-hash.info/
- Ted
--
To unsubscribe from this list: send the line "unsubscribe git" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html