[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Sources of randomness
>Date: Thu, 2 Nov 1995 00:39:29 -0800
>From: [email protected] (Timothy C. May)
>Digitized video input, especially from something like a noisy channel (t.v.
>channel, for example), is quite likely to produce a lot more entropy bits
>per second than nearly any of us ever need. (One's PGP key could be seeded
>in a fraction of a millisecond, for example.)
My cable feed into my Mac, for example, has surprisingly little noise --
and it's only local noise (stuff only at my house, not available to the
eavesdropper) which counts as entropy.
> One of the basic ideas we
>have had, as Cypherpunks, is to encourage widespread methods. Any methods
>that need special hardware tend to not get widely used.
>
>Audio, video, disk timing, and all sorts of other sources of physical
>randomness are useful to have, but most people either won't have the right
>configuration or won't configure their systems so as to use their
>configuration.
Most Macs and PCs have audio inputs. Most of those are mono,
unfortunately. [The numeric difference between two stereo mics is
especially hard for an eavesdropper-wannabe to predict/compute, assuming
the room isn't silent.] However, if the eavesdropper doesn't have a mic in
your room, there's still some entropy available on the mono channel.
Meanwhile, my old Sparcstation 1 had an A-D which, when no mic was
connected, gave about 1 bit/second of entropy. (The newer Sparc here gives
solid 0's with no mic.)
Recorded audio is useless as entropy, of course.
Almost all computers have a mouse and a normal signature, hand-written with
a mouse, has great gobs of noise. (I'm still working on the little PC
program to measure this -- but preliminary results show a minimum of 1 bit
of noise per mouse sample -- or 200 bits per signature. Final results may
get higher entropy rates, but I'll wait for the real results before
claiming that.)
+--------------------------------------------------------------------------+
|Carl M. Ellison [email protected] http://www.clark.net/pub/cme |
|Trusted Information Systems, Inc. http://www.tis.com/ |
|3060 Washington Road PGP 2.6.2: 61E2DE7FCB9D7984E9C8048BA63221A2|
|Glenwood MD 21738 Tel:(301)854-6889 FAX:(301)854-5363 |
+--------------------------------------------------------------------------+