[Cryptech Tech] Alpha board BOM and PCB design requirements

[Fredrik Thulin]

On Monday, March 09, 2015 11:59:30 PM Randy Bush wrote:
> yay!!!  fantastic!!!
> 
> why is keystore memory not mounted?

The latest rounds of discussions (on list, after Jakob and Joachims use cases 
IIRC) seemed to be that the keys would be stored (wrapped) in the ARM external 
storage. Only master key (unwrapping key) would be stored in the Master Key 
Memory connected to the FPGA.

> > The memory is connected to the FPGA with SPI interface. The memory is
> > connected to the FPGA with the same SPI interface.
> 
> some doubling here

Right, changed to "The MKM is connected to the FPGA with SPI interface. The 
MKM is connected to the Tamper Sub System with the same SPI interface. "

> entropy source should have link to schematic

Yes - I was thinking we (ermm, I) would make a separate schematic with the 
exact parts of the existing schematic that would go onto the Alpha PCB. Not 
done yet.
 
> why not spec a much larger sd card?  2g seems a bit small

I guess our fingers aren't tall enough to reach higher up into the air? =). No, 
seriously, what would be the use case (asked as a way to derive what size is 
actually needed, on the Alpha board - is it logs, OS, gazillions of keys or 
what)?

> external ddr3 is how large?

What do you suggest?

> thank you, thank you, thank you.

You are welcome. Thank you.

I spotted another error in the text:

> The Tamper Sub System controller can read and write to the memory

This was a typo. The intent was that the Tamper MCU should only be allowed to 
write to the Master Key Memory. Changed "can read and write" into "can only 
write".

/Fredrik