[Cryptech Tech] Dieharder test of Cryptech RNG data

[Fredrik Thulin]

On Saturday, April 04, 2015 01:18:46 PM Павел Шатов wrote:
> On 04.04.2015 10:56, Joachim Strömbergson wrote:
> > Aloha!
> > 
> > Basil Dolmatov wrote:
> >> I need schematic, description and bunch of data for test.
> > 
> > And by schematic you actually mean block/functional diagram I hope, not
> > electrical schematics?
> 
> What's wrong with electrical schematics? I would like to have a look at
> it too. To be honest, I did not completely understand Fredrik's
> explanation of how avalanche entropy source works. In his letter he
> wrote, that -15V was used to power it, but in the attached schematics
> (http://wiki.cryptech.is/raw-attachment/wiki/AlphaBoardComponents/alpha_boar
> d_noise_source.pdf) +12V is shown instead.

I'm glad you asked so we can sort out the confusion.

The -15V refers to this hardware (software alongside in the repository)

http://wiki.cryptech.is/browser/user/ft/stm32-avalanche-noise/hardware/rev09/rev09-sch.pdf

The Novena entropy noise source board which I believe is you have is almost 
identical to this, and I've attached the schematics.

> I also don't quite understand why charge pumps are used? As far as I
> know, they have very limited output current, while during avalanche
> breakdown large current flows through transistor. Is this okay?

There is a current limiting resistor, which probably also plays an important 
role in preventing fast aging of the noisy diode/transistor.

I don't remember the exact value, but I think the current consumption was 47 
mA for the avalanche circuitry at -15V.

> What signal is fed into FPGA, btw? TP19 ("AMPLIFIED")? Is it okay to
> feed analog signal into digital input buffer?

Right, I have a Schmitt trigger on the AMPLIFIED signal to digitize the signal 
in the current Novena board. That might be appropriate to add for the Alpha 
board too. You are a good proof-reader - thanks.

/Fredrik
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