Re: DES-Busting Screen Savers?

[frantz@netcom.com (Bill Frantz)]

At  2:28 AM 7/24/96 -0700, Steve Reid wrote:
>On the subject of choosing keys randomly, rather than dividing up the
>keyspace... 
>
>This seems like a very good idea to me.
>
>One potential problem is actually choosing the random keys. Have to be
>able to get entropy at a fast rate, and/or use a good PRNG.

I think you chose your starting place in the key space and then proceed
sequentially from there.  However, if it turns our that gray code
increments of the key can reduce the key setup time, then you would want to
use that ordering of the key space for the "next" key to try.

Another possibility is to work in randomly chosen blocks of 1000 to
1,000,000 or so keys.  This approach would reduce the cost of getting good
random numbers to manageable levels.


-------------------------------------------------------------------------
Bill Frantz       | Cave ab homine unius lebri | Periwinkle -- Consulting
(408)356-8506     |  [Beware the man of one    | 16345 Englewood Ave.
frantz@netcom.com |   book]  - Anonymous Latin | Los Gatos, CA 95032, USA