Roger, I would like some details about your hardware RNG, if you could, including how you were reading the random value. I had the impression you were taking one bit at a time. What did you mean when you said: "I just got a 3 standard deviation at a 1000000 sample..."? What statistical testing did you do? I used the chi-square test on 8-bit values (255 degrees of freedom), and also computed the probablility for the chi-square statistic. I programmed the runs-up and runs-down tests as suggested by Knuth, and computed the chi-square for those as well. Finally, I counted the numbers of 1 and 0 bits, and the number of times 1 followed 0, 0 followed 1, etc. I didn't do the autocorrelation test. If you have any code for that, I would appreciate having it. I'm not sure what you mean by "...the derevitives of the sequence..." What is that? I suppose these gadgets could be useful for those who want the absolute security of the one-time pad, and can exchange disks securely. With disks holding 1.44 meg now, it could be practical. John A. Thomas b858jt@utarlvm1.uta.edu 75236.3536@compuserve.com PGP public key available.