[Cryptography] The world's most secure TRNG

Bill Cox waywardgeek at gmail.com
Tue Oct 7 21:59:28 EDT 2014

On Wed, Oct 1, 2014 at 3:53 AM, Clemens Ladisch <clemens at ladisch.de> wrote:

> Bill Cox wrote:
> > On Tue, Sep 30, 2014 at 7:03 AM, Natanael wrote:
> > > Den 30 sep 2014 09:55 skrev "Philipp Gühring":
> > > > So from a marketing point of view you should put a whitener on the
> > > > part.
> > >
> > > Yes!
> >
> > Thanks for that suggestion.  I'll whiten with some of the leftover gates.
> > How to do a decent job sounds like a fun problem.
> You need custom drivers for this device anyway, so it might be a better
> idea to let the software do a decent job.  (You might want to add to the
> USB packets a header with the current settings and the actual amount of
> entropy; in that case there is less danger that anybody thinks this data
> is a perfectly random bit stream.)
> And why are you calling it a whitener instead of a randomness extractor?
> The former name could imply that the output looks random, but has less
> than 100% entropy.
> Regards,
> Clemens

I've reduced the BOM for the parts (not board/assembly/test yet) from about
$7.00 to $2.60.  Unfortunately, my bandwidth dropped from 1MiB/s to maybe
25KiB/s.  Also, I was convinced by the argument above that I had to write a
driver anyway, so why not put the whitener there?  I call it a whitener
because that's the accepted term... frankly I think that term sucks, but I
have gripes about a lot of common terms like this.

I removed the FPGA from the design and now only have a USB-to-FIFO chip
acting in bit-bang mode to control the infinite noise multiplier, which is
much slower.  I think you guys were right to have me focus on cost.  More
people will copy my $1.10 in parts (without the USB controller) even if it
generates only 25KiB/s, than ever would copy my $5.50 1MiB/s TRNG.

I've got my $1.60 USB interface chip to configure Lattice ICE40 FPGAs,
which only cost about $1.50 (both in quantities 1,000).  It seems like that
would be a fun proto-board by itself.  A $5 FPGA USB hacker board might be
fun... The Lattice tools to configure it runs a free copy of Synplify Pro,
which looks almost exactly like it did when I stopped working on this tool
in 1998.  The schematic generator seems to be about the same as I left it,
though there was a really good guy making amazing improvements for a while
after I left.  Time seems to have degraded it back to my version.

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