[Cryptech Tech] Some measurement results for FPGA with avalanche entropy source

[Bernd Paysan]

Am Samstag, 6. September 2014, 09:52:05 schrieb Randy Bush:
> > Not too shabby.
> 
> indeed!
> 
> > I would also like to test Benedicts board.
> 
> < fantasy = on >
> 
> can we show up at ches with a full chain on the novena based on two
> external sources (fredrik's and benedikt's) and N internal ROs?  and be
> able to run dieharder?

The internal ROs won't pass dieharder without additional stuff, due to the 
bias.  I've been thinking about mixing them all together through one LSR, 
which would work like this, with ro being 32 ring oscillator outputs (flip-
flops, sampled each cycle):

  reg [31:0] mix;

  always @(posedge clk)
     mix <= ro ^ { mix[30:0], ~mix[31] };

and sampling mix every multiple of 64 cycles (better accumulate for 128 
cycles).

This function eliminates biases (after 64 rounds, we have 32 inverted and 32 
non-inverted samples xored together in each bit), and still is simple enough 
that all real failures of the ring oscillators (like aligned oscillation or 
insufficient jitter) will show up.

> i am not even sure we know how to get two external sources into the
> novena at the same time.

We need this differential-to-single-ended board, and then several external 
sources should be no problem at all.

-- 
Bernd Paysan
"If you want it done right, you have to do it yourself"
http://bernd-paysan.de/
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