[Cryptech Core] alpha schematics

Pavel Shatov meisterpaul1 at yandex.ru
Fri Dec 18 10:54:16 UTC 2015


On 17.12.2015 11:14, Joachim Strömbergson wrote:
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA256
>
> Aloha!
>
> Pavel Shatov wrote:
>> I'm also afraid, that "Analog switch to boot FPGA from config memory,
>> or from ARM" is misleading.
>>
>> FPGA has built-in config memory, that is volatile. There must be
>> some external non-volatile memory, where the bitstream will be
>> stored. Every time FPGA is powered up, config bitstream must be
>> loaded from that external memory into FPGA's internal volatile
>> latches. Now FPGA can try do this itself automatically (master mode),
>> or it can just sit and wait for someone to send it the bitstream
>> (slave mode).
>>
>> Novena has the second variant. The bitstream is stored on the SD
>> card, when we run configure script i.MX processor reads the bitsream
>> from disk and directly sends it to the FPGA to configure it.
>>
>> If I understand everything correctly, we want Alpha board to
>> implement the first variant. The FPGA will automatically load
>> bitstream from config memory. STM32 processor will not be able to
>> directly configure FPGA anymore, it will only be able to re-write
>> config memory with new bitstream (if allowed by insertion of jumper)
>> and tell FPGA to re-load bitstream from config memory. Is this what
>> we actually want?
>
> That was at least my intention. Allowing the CPU to write new configs
> and kick the FPGA into reconfigure itself. And then with the jumper
> protect the config in the external config memory from being overwritten
> when the system is used in operation.
>
> This allows us to have a TRNG starting up automatically after power up
> (and release of reset), having the FPGA handling the MKM without the CPU
> configuring the FPGA, talking to the tamper chip etc. The FPGA becomes a
> more independent part of the system.


Good, this will simplify schematics a bit.


--
With best regards,
Pavel Shatov


More information about the Core mailing list