Re: Hardware-random-bits interface

[tcmay@got.net (Timothy C. May)]

At 3:17 PM 11/15/95, David K. Merriman wrote:
>At 02:31 PM 11/14/95 -0800, you wrote:
>>I've been thinking about physically random bits recently, so
>>I'd like to offer a simple, easily implementable interface to a
>>source of such bits, along with a design sketch using a common
>>radio receiver chip as the noise source.
>
>It sounds like a fairly decent idea, _as long as you shield the bejeebers
>(technical term :-) out of it_. Otherwise, anybody with a signal generator
>could skew your numbers however they saw fit: any component lead can act as
>an antenna, no matter now small that lead is.

But if you "shield the bejeebers out of it," then all the radio receiver
generates is whatever signal manages to sneak through--which, ironically,
would make it _easier_ for an outside attacker to drive--and some amount of
internal receiver/amplifier noise, such as the Johnson noise talked about
here. (Every receiver has an "equivalent noise temperature," recall.)

And if one is left with only internal noise, why not simply use a nice
clean source like a Zener diode?


--Tim May

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