[Cryptech Tech] Alpha board block diagram v0.001

[Benedikt Stockebrand]

Hi Pavel and list,

Павел Шатов <meisterpaul1 at yandex.ru> writes:

> Benedikt, what do you think about CP2104 chip from Silicon Labs?

I don't know---when I built the ARGGH board the FTDI stuff was the most
widely known in the Maker community and the only one readily available
from my usual distributor (Reichelt).

I could have ordered a Prolific chip or whatever from Digikey (I think),
but with me putting much more emphasis on easy DIY building that was
undesirable---Digikey charges a "low volume" surcharge that makes it
absolutely clear they don't want orders worth less than a couple hundred
USDs/Euros.

> It is slower than FT232, but they offer open source Linux driver for
> it.
>
> Btw, as far as I know there are alternative open source FTDI drivers:
> http://www.intra2net.com/en/developer/libftdi/
> Can we use them?

It's not a problem with the drivers at all, but with the chips
themselves.  If you haven't heard of "FTDIgate", please look up "FTDI"
on Wikipedia, last time I checked they had a concise and really decent
summary of what happened.

The problem I have with these chips is that they can be reprogrammed
from the outside without any need of physical access, like an "enable
reprogramming jumper" or dedicated programming pins.

Aside from that, from the event it is obvious that there are
microcontroller based implementations sold as counterfeit FT232's, so
building and slipstreaming a "functionally enhanced" chip (i.e. one with
a backdoor) to us is unnecessarily simple if an attacker has the right
connections there.


Cheers,

    Benedikt

-- 
Benedikt Stockebrand,                   Stepladder IT Training+Consulting
Dipl.-Inform.                           http://www.stepladder-it.com/

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