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SubjectRe: [rc4-amd64] RC4 optimized for AMD64


On Mon, 1 Nov 2004, dean gaudet wrote:

> On Mon, 1 Nov 2004, Marc Bevand wrote:
>
> > I have just published a small paper about optimizing RC4 for
> > AMD64 (x86-64). A working implementation is also provided:
> >
> > http://epita.fr/~bevand_m/papers/rc4-amd64.html
> >
> > Kernel people may be interested given the fact that Linux
> > already implements RC4.
>
> you've made a non-portable flags assumption:
>
> > dec %r11b
> > ror $8, %r8 # (ror does not change ZF)
> > jnz 1b
>
> the contents of ZF are undefined after a rotation... most importantly
> they differ between p4 (ZF is set according to result) and k8 (ZF
> unchanged).

ack... it's too early on a monday morning -- i misread the documentation.
this ZF assumption is actually defined and portable... still kind of ugly.
how much benefit do you see?

-dean
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