Bugtraq mailing list archives
RE: /dev/random is probably not
From: "David Schwartz" <davids () webmaster com>
Date: Thu, 7 Jul 2005 13:46:54 -0700
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.It doesn't look like a good source of entropy. At least it wouldn't withstand an active attack during this activation phase.- Bob Foxworth, GSEC, CISSP
What "active attack" allows an attacker to predict the jitter between the network card's quartz oscillator and the frequency multiplier that generates the CPU clock? The low order bit of the TSC at the time a packet is received is believed to be almost purely a function of this jitter, for typical x86 CPUs at normal temperatures. DS
Current thread:
- Re: /dev/random is probably not, (continued)
- 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)