[RC5] keyrate stabilizing?

Orthanc orthanc_duo at hotmail.com
Tue Oct 23 02:29:21 EDT 2001


Sorry to be the one to point this out again.
shifts multiply and divide by 2.

Rotates cannot be used for this. Only use I know of is in introducing
randomness into ordered data for encryption of hashing.

Orthanc

----- Original Message -----
From: "Test Man" <mr_nobby at yahoo.com>
To: <rc5 at lists.distributed.net>
Sent: Monday, October 22, 2001 7:34 PM
Subject: Re: [RC5] keyrate stabilizing?


> Is it really true that some CPUs do not have rotate
> instructions? I mean, a rotate is effectively a shift
> register - which is one of the fundamental blocks of
> digital electronics. Even the Sinclair ZX80 had one!
> And rotate/shift instructions are a very quick way of
> multiplying or dividing by powers of 2.
>
> Sorry if I'm out of place on this one or if it has
> already been covered, but I've just joined the list.
>
> --- Zorba the Hutt <zorbathut at uswest.net> wrote:
> >
> > Yeah, but how much CPU does SSL/SSH really take up?
> > I used SSH a little on
> > my P166, and I didn't exactly have to shut down all
> > my programs. Not only
> > that, but with the ever-tightening encryption laws,
> > perhaps focusing on
> > making the (already-fast) encryption even *faster*
> > isn't a good use of their
> > time.
> >
> > The people who use CPU power are, for the vast
> > majority, gamers,
> > programmers, artists, and people who need lots of
> > servers. The only one of
> > those who cares about rotating bits is the last, and
> > only if they're doing
> > encryption.
> >
> > It just plain isn't worth it.
> >
> > -Zorba
> >
> > ----- Original Message -----
> > From: "Christopher Hicks" <chicks at chicks.net>
> > To: <rc5 at lists.distributed.net>
> > Sent: Saturday, October 20, 2001 10:40 AM
> > Subject: Re: [RC5] keyrate stabilizing?
> >
> >
> > > On Fri, 19 Oct 2001, Dan Sugalski wrote:
> > >
> > > > While rotates are useful in this case, and a few
> > other isolated
> > > > places, this is such an edge case that it's just
> > not worth the silicon
> > > > that it'd take to implement a rotate
> > instruction. Not having one
> > > > simplifies the ALU a bunch, and that speeds up
> > the core and leaves
> > > > more room for other things.  Even if a CPU fakes
> > it, like the newest
> > > > intel and AMD chips likely do, you still get a
> > win. (Heck, if all
> > > > tossing rotate out got you was another line in
> > your L1 cache it'd be
> > > > worth it...)
> > >
> > > In this day and age I would think that working
> > well on encryption would be
> > > more of a priority for CPU designers.  It hardly
> > seems like an edge
> > > application to someone that uses ssl and ssh on a
> > daily basis.
> > >
> > > --
> > > </chris>
> > >
> > > Neither sweat, nor blood, nor frustration, or
> > lousy manuals
> > > nor missing parts, or wrong parts shall keep me
> > from my task.
> > >
> > > --
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> > >
> > >
> >
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> >
>
>
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