Re: Simple Hardware RNG Idea

Simon Spero writes:
....
> What about a beam of high intensity ionising radiation aimed at the
> detector?
....
You presumably use the oddness of the count for your random bit in some
predetermined time interval. External radiation can change, but not bias
the parity. If the counter saturates, the counter may be biased towards one
parity but the software can easily detect saturation presuming it gets the
count.

You can use the source in a smoke detector.

On Thu, 5 Oct 1995, Norman Hardy wrote:

> Simon Spero writes:
> ....
> > What about a beam of high intensity ionising radiation aimed at the
> > detector?
> ....
> You presumably use the oddness of the count for your random bit in some
> predetermined time interval. External radiation can change, but not bias
> the parity. If the counter saturates, the counter may be biased towards one

Hmmm. But isn't this method slightly biased? If the probability of  N 
events < the probability of N+1 events, wouldn't you need a large number 
of events per bit to make the bias insignificant? 

The measurement I was thinking of (which would have been susceptible to 
the external attack) was to measure the interval between events, and 
convert that to a uniform distribution. That's probably trying to get too 
many random bits per event, but does let you use much lower level sources.

BTW, I was just having dinner with a bunch of guys from HP labs in 
Bristol, UK, and the subject of hardware RNGs came up. The idea of 
Strontium-90  as the next computer consumable has a certain appeal- the 
designating brandname is "Omnisource".

 "Are you having trouble scintillating? With Omnisource, you can scin till
  dawn!" 

Simon