[sdiy] Lockout / DRM chips?

Fri Sep 11 06:51:51 CEST 2026

How is a compromised module defined & detected?
How would the repudiation information reach a compromised module? or to
modules connected to the compromised module?

I'm sure there are complexities, but mixing coded noise into the outputs
doesn't seem especially difficult. If the outputs are already digital, then
you need to find a synchronization side channel.  If the outputs are
analog, modulate sync information in a frequency band outside what you were
planning on transmitting ... if you're already satuating the analog i/o
bandwidth, then find a different side channel.

PS. Note that this doesn't really prevent clones.  It simply makes the new
equipment incompatible with *everything* else.  Which doesn't sound very
appealing to me as a consumer, but maybe the easy-to-clone yet
intrinsically-awesome capabilities of modules in this new format will
change my mind.

PPS. If you're depending on modules being connected to the internet for
repudiation data, then authorization is what the world generally uses.
 Works very well.  Again, consumers generally hate it.

On Thu, Sep 10, 2026 at 9:26 PM cheater cheater <cheater00social at gmail.com>
wrote:

> While technologically difficult it's also probably satisfactory, but
> you'd probably need to be able to repudiate compromised devices /
> licenses as well.
>
> On Fri, Sep 11, 2026 at 6:19 AM David Kantowitz <dkantowitz at gmail.com>
> wrote:
> >
> > Would this example approach satisfy your needs:  every output is mixed
> with wide-band PRNG noise and only "in family" modules have the algorithm
> to filter that noise from their inputs.
> >
> > On Thu, Sep 10, 2026 at 9:09 PM cheater cheater <
> cheater00social at gmail.com> wrote:
> >>
> >> > Honestly, it's a bit hard to point you in the right direction without
> understanding what you actually want to do.
> >>
> >> Ultimately the goal is as follows.
> >>
> >> Situation: A new physical format, let's say for modular synthesizers
> >> or audio effects, is created.
> >> Problem: how to lock out a specific manufacturer that clones devices
> >> created by others, so they don't shit up this format as well?
> >> Solution: some form of hardware authorization and authentication
> >>
> >> Purpose of the discussion: The first part can be something myself and
> >> some others are planning, or it could be something that a completely
> >> different group of people are doing and they could use what's been
> >> learned here as basis for safeguarding their business from parasitical
> >> manufacturers
> >>
> >>
> >> On Thu, Sep 10, 2026 at 10:02 PM David Kantowitz <dkantowitz at gmail.com>
> wrote:
> >> >
> >> > Not really. Search for "secure microcontroller" at the NXP website.
> The detailed manuals (at least for NXP) usually require an NDA w/ NXP, but
> a 2-page summary sales sheet should be available.
> >> >
> >> > A lot of microcontrollers (not just NXP) have features like: 'secure
> boot', 'secure element', 'secure memory', 'trusted module', 'trusted
> execution', etc.  ARM has TrustZone that a lot of manufacturers use.  Some
> combination of those features could do what you want.
> >> >
> >> > Honestly, it's a bit hard to point you in the right direction without
> understanding what you actually want to do.   ... and based on my earlier
> emails, what you described as wanting to do doesn't really make sense to me
> in a commercial context.  There are significant costs involved in building
> even vaguely secure hardware.  An example of the stupid shit that happens
> ... units were keyed at Key Injection Facility, then shipped to the user
> site, units started to arrive in the tamper state with no keys .. queue 6
> month parade of units back and forth ... eventually we figure out that a
> software bug wasn't putting the cpu into a low enough sleep state and the
> supercap keeping the keys alive was drained in transit.  I can't even bear
> to describe how stupid the spares situation became.
> >> >
> >> >
> >> >
> >> > On Thu, Sep 10, 2026 at 11:51 AM cheater cheater <
> cheater00social at gmail.com> wrote:
> >> >>
> >> >> Thanks, David. That's some good info. Can you point to some recent
> >> >> devices that are available on the market?
> >> >>
> >> >> On Thu, Sep 10, 2026 at 7:22 PM David Kantowitz <
> dkantowitz at gmail.com> wrote:
> >> >> >
> >> >> > BOM cost was single digit USD.  Essentially it was a way to audit
> licensing fees through an electronic component based supply chain.
> >> >> >
> >> >> > What you're describing are key rolling and key injection.  You can
> look at current practices for payment terminals, but honestly those are
> made-by-committee unions of the individual company's own practices.
> >> >> >
> >> >> > We used two basic approaches to secure the cryptographic root:
> >> >> >   1. 'Base' key injection key that's used only to load
> site-deployment keys.  Those keys were secured by obscurity.
> "Steganographic methodology" when we wanted to sound like experts.
> >> >> >   2. Shipping units to a secure key injection facility.  Use
> tamper evident bags when you want a fancy audit trail.
> >> >> >
> >> >> > Site keys are stored in something physically tamper-proof.  As a
> simple example (ie. what was done 20 years ago):
> >> >> >   - make a PCB sandwich.  all components on inside, no traces on
> outside of PCB.  single power & serial port on outside. a plastic ring goes
> around the edge. bolot he sandwich together.
> >> >> >   - electrical connection between the two boards via pin headers
> >> >> >   - put key in static RAM (not flash, not DRAM)
> >> >> >   - SRAM on board A, battery on board B
> >> >> > If someone opens the sandwich and the site keys lose power.  Back
> to (1) or (2) above to restore site keys.
> >> >> >
> >> >> > Despite having microcontrollers with secure memory, much more
> physically complicated versions of the sandwich are still used today:
> >> >> >   (A) Detect the tamper.  (B) Destroy the keys.  (C) Restore the
> keys.
> >> >> >
> >> >> > Separately, everyone also builds in some method for key-rolling
> into their systems.  This handles the scenario you described: you believe
> the keys were actually stolen with malicious intent.  Personally, I've gone
> through customer witnessed testing of the key rolling, I've never seen a
> live system do a key roll.  It was simply too risky.  Instead we would
> maintain blacklists of cards & equipment.  This requires a system that is
> frequently online.
> >> >> >
> >> >> > On Thu, Sep 10, 2026 at 9:20 AM cheater cheater <
> cheater00social at gmail.com> wrote:
> >> >> >>
> >> >> >> I agree that the DRM is just one component of an otherwise healthy
> >> >> >> business strategy.
> >> >> >>
> >> >> >> Do you remember how much roughly the NXP chips added to your BOM?
> >> >> >>
> >> >> >> > This seems to be the arc of most cryptographically enabled DRM.
> >> >> >>
> >> >> >> I agree. I know about power monitoring, power glitching, and
> various
> >> >> >> other hardware attacks.
> >> >> >>
> >> >> >> One thing that I'm curious about is things like updating
> encryption,
> >> >> >> in order to be able to repudiate compromised keys, eg from
> >> >> >> manufacturers who have decided to start leaking them to companies
> who
> >> >> >> shouldn't have them. This would at least require some sort of
> secure
> >> >> >> vault with a machine of some sort inside, probably a VM.
> >> >> >>
> >> >> >> Cheers,
> >> >> >> D
> >> >> >>
> >> >> >> On Thu, Sep 10, 2026 at 6:09 PM David Kantowitz <
> dkantowitz at gmail.com> wrote:
> >> >> >> >
> >> >> >> > The closest "on topic" experiences I have are with the
> contactless payment (and ID) cards.
> >> >> >> >
> >> >> >> > To read/write Mifare cards, we had to include the Philips (now
> NXP) reader chip in our equipment: even though our own DSP/FPGA generated
> the RF modulation signals and we had our own implementation of the on-air
> data protocol stack.
> >> >> >> >
> >> >> >> > All the Philips chip contained was their proprietary
> shared-secret encryption algorithm.
> >> >> >> >
> >> >> >> > Two things happened over time:
> >> >> >> >   1. Researchers reverse engineered/discovered and published
> the exact proprietary cryptographic algorithm.
> >> >> >> >   2. Various key recovery techniques were possible through
> either defects in the protocol implementation or techniques like power
> monitoring (which you can also think of as an implementation defect).
> >> >> >> >
> >> >> >> > This seems to be the arc of most cryptographically enabled DRM.
> >> >> >> >
> >> >> >> > The Philips chips were generally easy to use and the
> integration cost was more a one-time expense.  Still they added to the BOM
> cost.
> >> >> >> >
> >> >> >> > Even after the system was broken we continued to use them: it
> was the easiest way to vouch to our customers that our equipment was
> compatible with Mifare cards.  That compatibility was necessary because, by
> then, out customers had money sunk (ie. millions) into cards.
> >> >> >> >
> >> >> >> > Briefly off topic: that 10+ year experience taught me that
> DRM-like capabilities are small (nearly irrelevant) technical components in
> a broader commercial strategy ; figure out the strategy first and then use
> DRM as a temporary stepping stone in that strategy.
> >> >> >> >
> >> >> >> >
> >> >> >> >
> >> >> >> > On Thu, Sep 10, 2026 at 12:41 AM cheater cheater via Synth-diy <
> synth-diy at synth-diy.org> wrote:
> >> >> >> >>
> >> >> >> >> David, Mike,
> >> >> >> >> Please start a separate thread, this isn't what this thread is
> about.
> >> >> >> >>
> >> >> >> >> Thanks.
> >> >> >> >>
> >> >> >> >> On Thu, Sep 10, 2026 at 8:58 AM David Huss via Synth-diy
> >> >> >> >> <synth-diy at synth-diy.org> wrote:
> >> >> >> >> >
> >> >> >> >> > The idea to do some sort of multichannel modular via digital
> cables is not exactly new and not exactly something that isn't obvious.
> >> >> >> >> >
> >> >> >> >> > Technically such a thing is already done with ADAT/Toslink
> optical cables and many audio interfaces use it to allow users to add more
> I/O channels.
> >> >> >> >> >
> >> >> >> >> > So the main obvious question is why we haven't seen
> something like this widely used in the modular world?
> >> >> >> >> >
> >> >> >> >> > To me the answer is that the simplicity of the concept is
> unbeatable: Everything is just a voltage versus time, one signal per cable,
> what you see is what you get. All while being reliable, cheap to implement,
> cables are cheap, clocking is not an issue, it is conceptually clear, etc.
> >> >> >> >> >
> >> >> >> >> > The two useful applications of multi-channel cables I see
> are: (1) polyphonic modules where patching up 4+ cables is annoying and
> takes up valuable panel space and (2) breakout boxes for multichannel
> connections between racks (e.g. via Ethernet).
> >> >> >> >> >
> >> >> >> >> > Of course I could envision cool systems with multi-channel
> cables, but I am not sure it is really worth the extra complexity to make
> them digital. By that point one can ask, why not just run everything on a
> computer and make a patch-cable controller panel that just reads out the
> patch connections, knob positions etc and controls a big virtual modular.
> >> >> >> >> >
> >> >> >> >> > On September 9, 2026 11:44:34 PM UTC, Gordonjcp <
> gordonjcp at gjcp.net> wrote:
> >> >> >> >> > >On Wed, Sep 09, 2026 at 07:31:21PM +0200, cheater cheater
> via Synth-diy wrote:
> >> >> >> >> > >>
> >> >> >> >> > >> So, there's good news and bad news. The bad news is that
> I can't go
> >> >> >> >> > >> into specifics, but there are good reasons to expect a
> new modular
> >> >> >> >> > >> format showing up sometime in the not extremely distant
> future.
> >> >> >> >> > >
> >> >> >> >> > >Good luck with that.
> >> >> >> >> > >
> >> >> >> >> > >How did you get one with your polyphonic modular idea with
> 24 channels of 24-bit 192kHz CV on a single 3.5mm jack?
> >> >> >> >> > >
> >> >> >> >> >
> >> >> >> >> > ________________________________________________________
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> >> >> >> >> ________________________________________________________
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