Making a wrapper around an electronic device which cannot be cut or penetrated without the device detecting it.
Assume the adversary has the device and is HIGHLY motivated to get into the electronics to disable it, how do the electronics detect and trigger if they try?
First thought: Numerous ultra-thin wires. If the adversary cuts a wire, it triggers. If he tries to bypass the wire before cutting into it, he doesn't know which wire on one end is the same wire on the other end. If he bridges wire 3 to wire 7 (for example) it triggers.
Problem: It's not entirely fool proof, if he can manage to strip the insulation off of the wires, he can scope them to figure out which is which and then bypass them one at a time, allowing him to cut into the device.
Second thought: Use a fiber optic strand. There's no way to splice into it without cutting it first.
So basically if you have a board with a fiber emitter and receiver. Connect one end of the fiber but not the other. Pot the board in epoxy except for a small hole where the other end of the fiber will be inserted, then wind the fiber around the potted board like a rubber band ball. Paint more epoxy over it to glue it in place. If there's a strap that needs to be guarded, string the fiber through the strap and then back to the board. and stick it into the hole in the epoxy to the receiver. Once the board flags a working connection, glue it in place.
@cjd Some sensitive equipment I've seen uses air pressure to prevent tempering, much like a jar of preserves.
Much like the jar's lid, a small capsule, connected to the electronics, lets air out without issues, as the assembly is sealed and vacuumed.
But if pressure is ever to increase, it bursts.
A couple of magnetic bits on a spring mechanism generate a current spike, overload and fry the electronics.
I'm sure it's more complicated than that, but this isn't my field, and I'm recalling things from years ago, but that's the general idea.
@cjd A worthy endeavor.
How about LIDAR, machine learning, or AI?
A camera inside the assembly that detects anything that differs from the expected state of things.
A tiny internal patrolman.
With the state of robotics these days, it shouldn't be too difficult.
There's an inner housing (3d printed) with 3 main cavities.
1. For the batteries and control board - sealed with epoxy from the factory.
2. An area where a spring loaded spool is housed, this spool will wind up the fiber once the activation pin is pulled
3. An area with a nozzle that injects epoxy into the zone with the spool.
There are a pair of fibers (strong jacketed cable) that come out of the housing, at the far end, the two fibers are spliced *together* so that a signal sent down one will come back up the other.
The far end (with the splice), is taken and fed back into the housing, where it's wound onto the spool. This creates a big loop from the housing back to the housing. The attack model is to put the loop over someone's head and pull the trigger pin, causing the spool to reel in, tightening up the cable.
There is of course a ratcheting mechanism so pulling on the spool side of the cable is not trivial, but in addition to this, pulling the activation pin causes epoxy to begin being injected into the spool housing. Once it has hardened (after about 10 minutes), the spool cannot turn in either direction (ever again).
The housing itself has a protection via another strand of fiber - this one unjacketed glass only. This strand is wound around the housing through designated channels in the outside surface, creating a criss-cross pattern that ensures any attempt to drill or cut into the inner housing will result in a trigger.
The inner housing is then painted with epoxy and encased in a two-piece outer shell which has just three holes, one for the pair of fibers coming out, one for the pair of fibers entering back in (to the spool) and one for the activation pin.
I'm imagining how one would build an absolutely diabolical weapon - an "exploding shock collar" which has a voice modulator that demands crypto payment within some # of hours - and which cannot be removed, not be police, FBI, CIA, Mossad, ANY ONE.