Random Number seeds, was RE: First computer with real-time clock?

John> On Mon, 2 Aug 2004, Paul Koning wrote: >> John> Computer-based ramndom number seed generation: John> I may at some point remember the machine/manufacturer, but I John> *do* recall tha one (perhaps Gummint-oriented?) device used a John> standard radio buried in it somewhere, tuned to a local John> station, the output of which was digitized and the seeds John> extracted from that... as I write this, IISTR that it was some John> kind of crypto-thingy... John> And just why would that be a bad idea? Remember this was back John> some years - your glib "these days" doesn't apply to 'them John> days'... in the 60's and 70's it was not trivial to develop John> 'real' random numbers, so various means were used to sample a John> physical source or 'randomness'. I have an audio whit noise John> generator (Grayson Stadler) that uses a 6CB4 tube with a small John> bar magnet in proximity to the envelope - this exacerbates the John> transit noise of the tube and produses a very nice 5 Htz to John> about 50 kHtz stream of chaos. Htz? You mean Hz? Noise diodes have been around for many decades, and certainly those would serve. So would resistors, and plenty of other things. What I was reacting to is the notion of a receiver "tuned to a local station". A radio signal is quite far from random, and if a cryppie were to use such a thing for generating keys he would be at serious risk of a successful attack. Now if you were to take a radio tuned to an unused channel, that would be somewhat better. But still it would be subject to unexpected biases from stations far away. A self-contained device such as an electrical noise source is much simpler AND it is much easier to prove that it has the right properties. By the way, re the AT&T random number generator whose properties were unproven -- these days, most of the designers of these devices *are* prepared to show adequate proof, as well they should of course. paul