On 7/4/05, Robert Foxworth <rfoxwor1@xxxxxxxxxxxxxxx> wrote: > At the last place at which I worked, a few years ago, a "random > number" was generated, and used in a FIPS 140-1 compliant > encryption device, by capturing 128 ethernet frames in sequence > from the local in-house network, gathering the LSB from the > arrival time of each frame, and using those values to generate > an encryption key. This was part of the "activation sequence" > which had to be done, once, on each such device. > > Any studies out there on the randomness of such a number? > At first glance a non-deterministic network would seem to be > able to generate a useful number for the key. OK, here's a quick set back-o-the-perl-script set of numbers. I sampled a million packets off one of my fairly well used internet links in 120.932020 seconds (according to tcpdump). I also sampled 209174 packets from my lan in 12507.724721 seconds (also according to tcpdump). Obviously I took the microsecond timestamp and extracted the low bit for further processing. From these samples I grabbed a few 128bit chunks from not-specially-selected offsets... internet: 1000000 bits counted, 499888 x 0, 500112 x 1, longest string 30 bits long was of 0 128 bits counted, 62 x 0, 66 x 1, longest string 10 bits long was of 1 128 bits counted, 57 x 0, 71 x 1, longest string 12 bits long was of 1 128 bits counted, 63 x 0, 65 x 1, longest string 10 bits long was of 1 128 bits counted, 68 x 0, 60 x 1, longest string 8 bits long was of 1 128 bits counted, 70 x 0, 58 x 1, longest string 8 bits long was of 0 128 bits counted, 76 x 0, 52 x 1, longest string 11 bits long was of 0 128 bits counted, 69 x 0, 59 x 1, longest string 8 bits long was of 0 128 bits counted, 61 x 0, 67 x 1, longest string 8 bits long was of 1 128 bits counted, 73 x 0, 55 x 1, longest string 11 bits long was of 0 128 bits counted, 74 x 0, 54 x 1, longest string 11 bits long was of 0 lan: 209174 bits counted, 104452 x 0, 104722 x 1, longest string 20 bits long was of 0 128 bits counted, 56 x 0, 72 x 1, longest string 8 bits long was of 1 128 bits counted, 58 x 0, 70 x 1, longest string 7 bits long was of 1 128 bits counted, 54 x 0, 74 x 1, longest string 8 bits long was of 1 128 bits counted, 64 x 0, 64 x 1, longest string 6 bits long was of 0 128 bits counted, 66 x 0, 62 x 1, longest string 8 bits long was of 1 128 bits counted, 55 x 0, 73 x 1, longest string 11 bits long was of 1 128 bits counted, 73 x 0, 55 x 1, longest string 8 bits long was of 0 128 bits counted, 63 x 0, 65 x 1, longest string 6 bits long was of 1 128 bits counted, 64 x 0, 64 x 1, longest string 8 bits long was of 1 128 bits counted, 68 x 0, 60 x 1, longest string 6 bits long was of 1 CK -- GDB has a 'break' feature; why doesn't it have 'fix' too?
