I have recieved a communication from a prefer-to-remain-annonymous source
that the press report I recall reading indicating a table-indexed function
is erroneous. This source asserted that the data is run through a von
Neumann-styled whitener. (The von Neumann whitener is the famous 00-> nil
01-> 0 10-> 1 11->nil technique). I say von Neumann-styled because it
generates on average 1 bit for every six input instead of 1 for every four
input. The problem with such a whitener is that it only guaranteed to work
if successive samples are time-domain independent. On a square-wave
generator such as a computer motherboard, this is not the case. As has been
mentioned, this is HIGHLY dependent upon board layout, and is likely to
change with board revisions.
Let me be clear: given that the RNG sets a register indicating data "ready",
there is a very good probablility that the thing does contain entropy. The
only question is how much to tell /dev/random. Without the design
specifications, it is hard to guess. (With them, it would still be a tough
job, beyond most of us on this list.)
Nathan
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