Thug writes,

The other possibility is to find a truly random RF source that has all the properties you want, the more important being that the >average< length of a homogenous bit run (0's or 1's) is around 4 or 5 bits.

"All the properties you want?" What you want is random, and nothing else! Random isn't "average bit runs of 4 or 5 bits". It isn't "nice white noise". It is TRULY RANDOM! You need to understand that the absolutely critical property for a one time pad bit-stream to have is this: given all previous bits seen, the probability that the next bit seen will be zero or one is exactly 0.5. What you need is a method for converting a biased random number stream (say, one where after a run of zeroes, another zero has high probability) into an unbiased one where the probability of the next bit being zero is exactly 0.5. Truncating runs to length 5 is an attempt at this, but a VERY BAD and cryptographically useless attempt. Does anybody remember a good recipe for converting a biased RNG into an unbiased one? I can't think of one off the top of my head, and that's what Thug's friend seems to need. This has been discussed at length in the literature. -- Marc Ringuette (mnr@cs.cmu.edu)