Re: Salsa20 altivec timings

tomstdenis_at_gmail.com
Date: 09/28/05


Date: 27 Sep 2005 17:32:24 -0700


xmath wrote:
> tomstdenis@gmail.com wrote:
> > xmath wrote:
> > > It's interesting to note that, due to unavoidable data-dependencies, a
> > > Salsa20 round must take at least 12 cycles, as absolute CPU-independent
> > > minimum (unless it offers combined add-rotate, rotate-xor, or xor-add
> > > instructions that execute in one cycle, something I've never seen in
> > > any CPU).
> >
> > ARM offers add-rotate but not the others [it can xor-rotate but not
> > rotate-xor].
>
> Interesting, didn't know that :-)

ARMs are crazy that way. I mean come on

A = (B + C) >>> D

Is a *common* operation :-)

To be fair

A = (B + C) >> D

Is common enough (e.g. signal average) so I guess supporting rotates
was not a far stretch.

> (Of course, to be relevant in this context it also needs to be able to
> do it on four 32-bit words in parallel in a single cycle, but still...)

There is a four-core ARM11 design out there ... hehehe I know what you
mean... the best ARM does [iirc] is SIMD on 32-bit values. So it's not
quite up to this.

Would be cool to see an FPGA implementation and compare it's size/speed
to other "typical" hardware ciphers.

Tom



Relevant Pages

  • Re: Guns make us safer
    ... The term "the people" as used in the second amendment means the very ... Justice, insure domestic Tranquility, provide for the common defence, ... They are all "arms". ... That generally means swords, knives and guns ...
    (alt.guitar.amps)
  • Re: OT: Right to bear arms
    ... my past comments on the second amendment: ... The question is *not* should we limit arms - the question is ... that the sorts of weapons protected were those ³in common use ... One weakness of the current wording is that new weapons are, clearly, not in ...
    (comp.sys.mac.advocacy)
  • Re: All or nothing for 2nd amendment
    ... It also meant cannons, ships armed with cannons and even private armed ... expected to appear bearing arms supplied by themselves and of the kind ... the kind in common use at the time." ... SCOTUS has done nothing of the kind ...
    (talk.politics.guns)
  • Re: This Could Be Any of Us, Anytime, Anywhere....
    ... the Letter of Marque was a government protection for that ... The 2A does not grant the right to keep and bear arms, ... that pool of citizenry by making it so the citizenry can not be ... so one looks at what were common arms used by the militia. ...
    (talk.politics.guns)
  • Re: Guns make us safer
    ... The term "the people" as used in the second amendment means the very ... Justice, insure domestic Tranquility, provide for the common defence, ... They are all "arms". ... That generally means swords, knives and guns ...
    (alt.guitar.amps)