[Cryptech Tech] Some thoughts and questions on the RNG strategy

[Joachim Strömbergson]

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Aloha!

Fredrik Thulin wrote:
> Can I have more than one, please?

More than one entropy source - yes! That is what I suggest that we shold
have.

More than one CSPRNG - maybe.


> To me, ideally, the cryptech HSM shouldn't be too set on any one
> entropy source or processing algorithm, although I realise that there
> might be both knowledge- and technical reasons to limit end users
> choices here.

I agree. The entropy collection sub system should be agnostic in regards
to what source you use. You will need to know the bitrate and there will
always be tweaking to map the inputs to the right pins etc. But other
than that, we _should_ be entropy source agnostic.

The issues we are discussing now is what to use in our
demonstrator/example implementation. And the reason why it is important
is that what we choose here will reflect on how the project is
perceived. And also I would assume that quite a few of possible Cryptech
implementers would borrow our entropy source designs if they seem
reasonably good.


> Joachim, you've previously slapped me silly when trying to draw ASCII
> diagrams of randomness processing =), but can't we have something
> functionally like this :
> 
> good source 1 ---> ChaCha ------+ +----> randomness good source 2
> ---> DRBG-CTR ----+

Sure, it is quite possible. I think it is a waste of resources having
two CSPRNGs and I think the CSPRNG should be seeded from more than one
source, but it is possible.


> I'm not going near the debate about what is a good source. I hope
> those could be modular rather than set in stone.

If my design is to prevail it sure will be.

- -- 
Med vänlig hälsning, Yours

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