Then use a 256 bit LFSR. It's still easier than using a radioactive source.

2^(256)-1 steps before it repeats.
--
Martin K

David VanHorn wrote:
> On 10/5/07, Martin Klingensmith <martin@nnytech.net> wrote:
>   
>> There are LFSR routines for PICs out there as well.
>>     
>
> Yeah, but they do repeat, eventually, and if you know the length, and
> seed, then you can work out what's next pretty quickly.   I have a 19
> bit implementation for the AVR, which I shift every time through the
> main loop, and when I use it, I grab a few bits from here, a few from
> there, making it harder to attack that way.
>
> But radioactive decay isn't that hard to get, and if someone can show
> how to un-randomize that, they have a Nobel waiting.
>   

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