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Re: Is there a process for secure firmware install/upgrade for device made offshore?

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Op Mon, 03 Jul 2017 19:16:32 +0200 schreef <jhnlmn@gmail.com>:
>> I meant that the program would check its own signature.
>> It can still be reverse engineered and patched to skip the checks, but  
>> this can be made arbitrarily difficult.
>
> Please, explain.
> As far as I can see, if a program can be both disassembled and patched  
> (which unencrypted JTAG allows),
> then anything is possible (and trivial), including skipping the check  
> entirely or replacing the signature.

If we're talking about a connected device, then a trusted external agent
could verify the signature. Preventing or faking this is non-trivial. But
let's assume a non-connected device.

Skipping the check could be made non-trivial by obfuscation techniques, I
guess.

Replacing the flash signature by your own is of course prohibitively
difficult when an adequate cryptographic algorithm is used. Replacing the
signature calculation algorithm by a function that just copies the known
flash signature is indeed trivial. However, if the signature would be
calculated by some peripheral when writing flash and could only be
compared, and not read out, then copying would be impossible.





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Is there a process for secure firmware install/upgrade for device made offshore? jhnlmn@gmail.com - 2017-06-23 21:34 -0700
  Re: Is there a process for secure firmware install/upgrade for device made offshore? Don Y <blockedofcourse@foo.invalid> - 2017-06-24 09:11 -0700
    Re: Is there a process for secure firmware install/upgrade for device made offshore? jhnlmn@gmail.com - 2017-06-24 15:27 -0700
      Re: Is there a process for secure firmware install/upgrade for device made offshore? Don Y <blockedofcourse@foo.invalid> - 2017-06-24 16:42 -0700
        Re: Is there a process for secure firmware install/upgrade for device made offshore? jhnlmn@gmail.com - 2017-06-24 19:26 -0700
          Re: Is there a process for secure firmware install/upgrade for device made offshore? Don Y <blockedofcourse@foo.invalid> - 2017-06-24 21:05 -0700
      Re: Is there a process for secure firmware install/upgrade for device made offshore? "Bill Davy" <Bill@XchelSys.co.uk> - 2017-06-25 10:37 +0100
        Re: Is there a process for secure firmware install/upgrade for device made offshore? Don Y <blockedofcourse@foo.invalid> - 2017-06-25 02:47 -0700
      Re: Is there a process for secure firmware install/upgrade for device made offshore? Hans-Bernhard Bröker <HBBroeker@t-online.de> - 2017-06-25 13:05 +0200
  Re: Is there a process for secure firmware install/upgrade for device made offshore? jhnlmn@gmail.com - 2017-06-24 21:59 -0700
    Re: Is there a process for secure firmware install/upgrade for device made offshore? Don Y <blockedofcourse@foo.invalid> - 2017-06-24 23:14 -0700
  Re: Is there a process for secure firmware install/upgrade for device made offshore? Dave Nadler <drn@nadler.com> - 2017-06-25 07:59 -0700
    Re: Is there a process for secure firmware install/upgrade for device made offshore? Don Y <blockedofcourse@foo.invalid> - 2017-06-25 10:43 -0700
      Re: Is there a process for secure firmware install/upgrade for device made offshore? Dave Nadler <drn@nadler.com> - 2017-06-25 12:43 -0700
        Re: Is there a process for secure firmware install/upgrade for device made offshore? Don Y <blockedofcourse@foo.invalid> - 2017-06-25 13:13 -0700
          Re: Is there a process for secure firmware install/upgrade for device made offshore? Dave Nadler <drn@nadler.com> - 2017-06-25 13:18 -0700
            Re: Is there a process for secure firmware install/upgrade for device made offshore? Don Y <blockedofcourse@foo.invalid> - 2017-06-25 13:53 -0700
              Re: Is there a process for secure firmware install/upgrade for device made offshore? Dave Nadler <drn@nadler.com> - 2017-06-25 14:05 -0700
                Re: Is there a process for secure firmware install/upgrade for device made offshore? Don Y <blockedofcourse@foo.invalid> - 2017-06-25 14:24 -0700
                Re: Is there a process for secure firmware install/upgrade for device made offshore? jhnlmn@gmail.com - 2017-06-25 16:46 -0700
                Re: Is there a process for secure firmware install/upgrade for device made offshore? Don Y <blockedofcourse@foo.invalid> - 2017-06-25 18:19 -0700
                Re: Is there a process for secure firmware install/upgrade for device made offshore? jhnlmn@gmail.com - 2017-06-25 18:57 -0700
                Re: Is there a process for secure firmware install/upgrade for device made offshore? Don Y <blockedofcourse@foo.invalid> - 2017-06-25 19:14 -0700
                Re: Is there a process for secure firmware install/upgrade for device made offshore? David Brown <david.brown@hesbynett.no> - 2017-06-26 09:26 +0200
  Re: Is there a process for secure firmware install/upgrade for device made offshore? jhnlmn@gmail.com - 2017-06-25 19:27 -0700
  Re: Is there a process for secure firmware install/upgrade for device made offshore? Stef <stef33d@yahooI-N-V-A-L-I-D.com.invalid> - 2017-06-26 08:56 +0200
  Re: Is there a process for secure firmware install/upgrade for device made offshore? jhnlmn@gmail.com - 2017-06-26 12:35 -0700
  Re: Is there a process for secure firmware install/upgrade for device made offshore? "Boudewijn Dijkstra" <sp4mtr4p.boudewijn@indes.com> - 2017-06-29 16:09 +0200
    Re: Is there a process for secure firmware install/upgrade for device made offshore? Dave Nadler <drn@nadler.com> - 2017-06-29 10:44 -0700
      Re: Is there a process for secure firmware install/upgrade for device made offshore? jhnlmn@gmail.com - 2017-06-29 20:22 -0700
        Re: Is there a process for secure firmware install/upgrade for device made offshore? "Boudewijn Dijkstra" <sp4mtr4p.boudewijn@indes.com> - 2017-06-30 13:44 +0200
      Re: Is there a process for secure firmware install/upgrade for device made offshore? Richard Damon <Richard@Damon-Family.org> - 2017-06-29 23:35 -0400
      Re: Is there a process for secure firmware install/upgrade for device made offshore? "Boudewijn Dijkstra" <sp4mtr4p.boudewijn@indes.com> - 2017-06-30 13:33 +0200
        Re: Is there a process for secure firmware install/upgrade for device made offshore? jhnlmn@gmail.com - 2017-06-30 17:11 -0700
          Re: Is there a process for secure firmware install/upgrade for device made offshore? "Boudewijn Dijkstra" <sp4mtr4p.boudewijn@indes.com> - 2017-07-03 12:05 +0200
            Re: Is there a process for secure firmware install/upgrade for device made offshore? jhnlmn@gmail.com - 2017-07-03 10:16 -0700
              Re: Is there a process for secure firmware install/upgrade for device made offshore? "Boudewijn Dijkstra" <sp4mtr4p.boudewijn@indes.com> - 2017-07-04 13:32 +0200
                Re: Is there a process for secure firmware install/upgrade for device made offshore? Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2017-07-04 13:40 -0400
                Re: Is there a process for secure firmware install/upgrade for device made offshore? jhnlmn@gmail.com - 2017-07-05 14:14 -0700
                Re: Is there a process for secure firmware install/upgrade for device made offshore? Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2017-07-05 19:51 -0400
                Re: Is there a process for secure firmware install/upgrade for device made offshore? jhnlmn@gmail.com - 2017-07-07 17:09 -0700
                Re: Is there a process for secure firmware install/upgrade for device made offshore? Chris <xxx.syseng.yyy@gfsys.co.uk> - 2017-07-17 18:52 +0000
                Re: Is there a process for secure firmware install/upgrade for device made offshore? Hans-Bernhard Bröker <HBBroeker@t-online.de> - 2017-07-17 21:38 +0200
                Re: Is there a process for secure firmware install/upgrade for device made offshore? jhnlmn@gmail.com - 2017-08-12 18:04 -0700
                Re: Is there a process for secure firmware install/upgrade for device made offshore? Paul Rubin <no.email@nospam.invalid> - 2017-08-14 09:53 -0700

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