chip-level randomness?

Bram Cohen bram at gawth.com
Sat Sep 22 12:46:43 EDT 2001


On Thu, 20 Sep 2001, Nomen Nescio wrote:

> If the internal circuitry did output a 60Hz sine wave then regularities
> would still be visible after this kind of whitener.  It is a rather
> mild cleanup of the signal.

It does mask patterns to an extent, possibly pushing them inside the
margin for error of the sample size you happen to use in a test.

> It doesn't seem right to object to them including a bias remover.
> They have done other things to reduce bias.  For example they use a pair
> of thermal resistors located next to each other on the chip and use the
> difference of the values from each of them, to reduce sensitivity to
> environmental influences.  This reduces bias, but should they have left
> the differencing out so that you could more easily measure a possible
> influence?

It's important to have the two of them to get a good estimate of the
amount of entropy it's outputting, although it would also be good if both
row values were available to the CPU, for diagnostic purposes if nothing
else.

-Bram Cohen

"Markets can remain irrational longer than you can remain solvent"
                                        -- John Maynard Keynes




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