[Cryptech Tech] Comments on Alpha board schematics

[Joachim Strömbergson]

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Aloha!

(Repeat in @tech)

We have previously talked about having the ability to turn off the
external entropy source.

I would suggest that the ability to turn the entropy source on or off is
given to the FPGA. (Which of course could expose the control via the
core API). If the control is done by the CPU or Tamper-MCU, then we
could easily end up reseeding the CPRNG using only the ring oscillator
based entropy provider. Having support for turning the entropy source
off ana on adds quite a lot of complexity in terms of warm up times and
startup testing vs starvation of RNG output and race problems.

When I look in Rev02, sheet 03 I assumed there would be a control signal
for this function, but I don't see it. Has it not been included?

- -- 
Med vänlig hälsning, Yours

Joachim Strömbergson - Alltid i harmonisk svängning.
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 Joachim Strömbergson          Secworks AB          joachim at secworks.se
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