[Cryptech Tech] Avalanche noise test boards

[Fredrik Thulin]

On Sunday, August 17, 2014 11:19:40 AM Benedikt Stockebrand wrote:
> Hi folks,
> 
> I've finished soldering up the boards, gave them a very quick test (one
> doesn't yet work) and just started a 24h test run on the first five of
> them.
> 
> Before I can ship them I need the snail mail addresses of everyone
> interested.  And I leave you to deal with customs:-)

(ALL: this is not just for Benedikt, please read it all)

Great! I'll be happy to get one. Please ship it to the SUNET office and I'll 
pick it up there.

  SUNET
  Tulegatan 11 2tr
  113 53 Stockholm
  Sweden

In the mean time, I've been working on my SPI-talking variant of it. It's been 
progressing nicely. I'm on the second iteration of my PCB, and I haven't found 
any physical bugs on this one =).

What I have is basically your generator core module, plus amplifier. I'm using 
a 2N3904 as noise source, and SMD components for the rest. I would be 
interested in any tips of SMD replacements for the 2N3904.

I have some questions regarding the BAT85 diode and it's intended effects on 
the amplifier, but I think it will be best for me to just compare your circuit 
(as you've built it) to mine first - in case my questions are just because I 
messed something up.

The first iteration of my build used a MAX232 IC to get +-12v. It wasn't very 
clean DC, with some spikes leaking over into the amplified noise. While I 
couldn't see that my Schmitt triggered input reacted to these spikes, it made 
me uncomfortable so I exchanged it for a LMC7660IM instead. This only gives 
+-5v, but that appears to be enough.

The MCU I'm currently using is a MSP430F2132 - because I've used that one 
before.

I have a Raspberry Pi compatible 2x13 header block interface, because that 
will allow me to do the SPI protocol development in Python.

I'm currently at the stitching-it-all-together stage, but I'd be interested to 
know what people think would be the best next step(s).

I only have three PCBs for now. I am going to ship one unit to Joachim and 
initially use the other two myself to study differences in individual units. 
I'm thinking it would be nice to make up some more boards after that to send 
out to others interested in helping with

  1) evaluating the randomness
  2) working on the functionality of the micro controller

and another idea is to develop a competing design using an STM32 MCU, in the 
name of chip diversity.

/Fredrik