Re: RC5 with FPGAs

I am currently interested in Achronix Semiconductor's FPGAs, which can
operate at 2 GHz

On 9/8/06, Olivier Meyer <[email protected]> wrote:
>
> What about the partial matches: how would one do that in an FPGA?
>
>
> On 9/7/06, david fleischer <cilantro_il-/[email protected] > wrote:
> >
> > That's interesting.
> > How does byte-reversed increment work?
> >
> > You suggest doing 6 rounds instead of 3. This to avoid
> > the penalty of storing the array until the key is
> > tested. But the RC5 algorithm is separated into
> > stages. You need all the data for the last step, so
> > you need at least to have gone through 2 rounds when
> > starting to encrypt the words.
> > How does the pyramid work?
> >
> > David
> >
> > --- Dan Oetting <dan_oetting-r9/[email protected]> wrote:
> >
> > >
> > > On Sep 6, 2006, at 12:07 PM, david fleischer wrote:
> > >
> > > > By the way, I'm not sure pipelining will bring you
> > > > great benefits in an FPGA. A back of the laptop
> > > > calculation tells me that you'll need
> > > approximately
> > > > 1Kbit of memory per key. This may mean that most
> > > of
> > > > the archirecture will be shoveling data back and
> > > forth
> > > > to the core.
> > >
> > > You don't have to store the data. You can recompute
> > > it. Instead of 3
> > > rounds with intermediate data stored between rounds
> > > you implement 6
> > > rounds in a pyramid so the correct data is provided
> > > to each stage as
> > > it's needed..
> > >
> > > > I also have a question, can someone help me figure
> > > out
> > > > the code in the source ANSI cores? I cannot
> > > understand
> > > > how the key increment is done. (that is to say, I
> > > see
> > > > what the code is doing, but I cannot figure out
> > > why
> > > > this does any good.)
> > >
> > > What the code is doing is incrementing the key in
> > > byte reversed
> > > order. Why this is done is because the calculations
> > > in the first 2
> > > 1/2 iterations of the first round then become
> > > constants so the loop
> > > can run a few keys per second faster. It won't help
> > > your hardware
> > > unless your design is fully pipelined so you can
> > > consolidate the
> > > first few sets of gates in each pipe. But you still
> > > need to implement
> > > the byte reversed increment to be compatible with
> > > the d.net project.
> > >
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> > >
> >
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>
>
>
> --
> -----------------------
> Olivier V. Meyer
> Congress shall make no law respecting an establishment of religion, or
> prohibiting the free exercise thereof; or abridging the freedom of speech,
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> petition the government for a redress of grievances.
>



-- 
-----------------------
Olivier V. Meyer
Congress shall make no law respecting an establishment of religion, or
prohibiting the free exercise thereof; or abridging the freedom of speech,
or of the press; or the right of the people peaceably to assemble, and to
petition the government for a redress of grievances.

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