[sdiy] analog loses another niche

[Dave Manley]

Veronica Merryfield wrote:
> It looks random to us now with our current knowledge and understanding, but one day when we have gained that knowledge and understanding, it would be predictable. 
>
> As I wrote the preceding posting it struck me that I should probably try to find something that from history that seemed random then but now isn't. I would imagine that the alchemists came across much that appeared random that is no longer such and I would imagine  that cave people couldn't make much sense of the stars.
>  
>
> On 2010-06-30, at 5:32 PM, Ian Fritz wrote:
>
>   
>> At 06:18 PM 6/30/2010, you wrote:
>>
>>     
>>> Hmmm - I am not sure that any source is truly random, just that we don't understand it enough.
>>>       
>> Why would you consider radioactive decay not to be random?  :-)
>>
>> Ian 
>>     
This implies: A return to a mechanistic universe? Predestination?

Thank the Flying Spaghetti Monster this is SDIY where we don't discuss 
such things.  :-)

So...I went and looked to see if Cavium had a patent on their TRNG, and 
indeed they do.  They use a bunch of ring oscillators (64 in one 
example), built out of very weak transistors, that are in a digitally 
noisy environment, thereby causing the oscillators to be extremely 
jittery, as a source of entropy.  They sample the oscillators and feed 
the result into a cryptographic hash such as SHA-1 (although the patent 
indicates you could use an LFSR).  The output of the cryptographic hash 
by it self is 'random' enough to pass most any test without the ring 
oscillators being fed into its state variable.

Rings a bell - doesn't someone in the sdiy community make an LFO whose 
output is the sum of six inverter based oscillators set to different 
frequencies?

-Dave