[Avila] How I can protect my program from not authorized reading via JTAG?

[Gordon Edmonds]

The difference with the MSP430 is that the software is held in internal
Flash in the microcontroller. It never needs to come out. If you were to put
software in the Flash on a GW2348 and "blow the fuse", the CPU would never
be able to read it.  That's why StrataFlash parts don't have security
fuses...

Gordon Edmonds
Gateworks Corporation
3026 S. Higuera Street
San Luis Obispo, CA 93401
805-781-2000
gedmonds at gateworks.com

-----Original Message-----
From: David Acker [mailto:dacker at roinet.com] 
Sent: Thursday, February 15, 2007 10:54 AM
To: Avila
Subject: Re: [Avila] How I can protect my program from not authorized
reading via JTAG?

Tim Harvey wrote:
> Nikita,
> 
> I've often thought about this as well.  There really isn't any way to do
this.  For starters, Gateworks programs the firmware on their boards using
the JTAG connector, so the connector will always be loaded on the board.  If
they were to move to pads/testpoints vs a physical connector this would make
it more difficult for someone not familiar with the board to read but
certainly not for the resourceful.  That said, removing the connector and/or
possibly resistors that may link that connector to the JTAG chain would make
it more difficult but not for the resourceful.
> 
> In my opinion, because you will never be able to keep someone from reading
the JTAG chain you would have to do something to encrypt/protect the info
from the flash they would be able to read which may require quite a bit of
bootloader/kernel modification.
> 
> Of course, regardless of the time/effort/$$ you put into protecting a
system if someone really wants to get into it and has the know-how they
probably will (ie, XBOX, XBOX-360, DVD CSS encryption, DVD-HD and Blueray -
these have all been hacked)
> 
> I wonder if there is a way to 'blow' the JTAG circuits on some/all of the
devices to make it impossible to read via JTAG (and impossible to re-program
a bricked board).
> 
> Tim

I used to use TI's MSP430 and http://www.softbaugh.com sold a JTAGer 
that would do exactly that for use in manufacturing.  Put the software 
on it and blow the fuse.
-Ack

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