[Cryptech Core] alpha schematics

[Pavel Shatov]

On 15.12.2015 1:53, Paul Selkirk wrote:
> I've just been looking it over, and had a few comments and questions.
>
> Most of the cores have a data_valid bit, which we currently have to poll
> for, through the register interface. It would also be great if we could
> somehow expose these directly to the MCU through one or more IRQ lines.
> I'm not sure exactly how this would work.

This should be really easy to do, actually. Basically, we just need to 
add one output port per core wrapper to expose internal valid signals. 
Given that we have many cores that we want to monitor, it may be a good 
idea to combine them into just one IRQ line using a multiplexor. This 
way we'll have a control register, that selects which core is connected 
to IRQ line.

> In Stockholm, we talked about having two USB interfaces - one for data
> exchange (keys, digests, etc), and one for the management console. On
> the dev-bridge board, one of these has morphed into a USB power outlet
> (although it's not clear why we'd want that, given that the board is
> only useful when plugged into the Novena). So could we please restore
> the management USB?

Yes, I remember this too, good catch.

> On sheet 2, there is a "Jumper deciding if FPGA/ARM/None should be
> allowed to turn off the entropy source (default On through pull-up)".
> It's not immediately clear why we would want to allow that.

Repetitive avalanche breakdown causes degradation of P-N junction in the 
noise circuit. As far as I remember, rather rough estimate of board's 
expected lifetime is around two years. At some point we thought, that it 
may be a good idea to power down the noise circuit, when it is not 
needed to extend board's lifetime. I don't know, whether we need this 
feature at all, and I also don't know what the control algorithm should 
be. Fredrik and I decided to just provide for this feature and discuss 
this issue on the tech list after we "go public".


Pavel