Bugtraq mailing list archives
Re: /dev/random is probably not
From: Chris Kuethe <chris.kuethe () gmail com>
Date: Tue, 5 Jul 2005 21:07:56 -0600
On 7/4/05, Robert Foxworth <rfoxwor1 () tampabay rr com> 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?
Current thread:
- Re: /dev/random is probably not, (continued)
- Re: /dev/random is probably not Francesco Messineo (Jul 12)
- Re: /dev/random is probably not Zow (Jul 04)
- Re: /dev/random is probably not Anton Ivanov (Jul 05)
- Re: /dev/random is probably not devnull (Jul 06)
- RE: /dev/random is probably not David Schwartz (Jul 05)
- Re: /dev/random is probably not Glynn Clements (Jul 05)
- Re: /dev/random is probably not ChayoteMu (Jul 06)
- Re: /dev/random is probably not Jack Lloyd (Jul 05)
- Re: /dev/random is probably not Alexey Toptygin (Jul 06)
- Re: /dev/random is probably not Chris Kuethe (Jul 06)
- Re: /dev/random is probably not Thomas (Jul 06)
- RE: /dev/random is probably not David Schwartz (Jul 08)