People worry about malicious chips in instances like this and I mean it's a valid concern but one method of attack I've always thought would be effective and extremely dangerous is strategic placing a component in a circuit that, if it fails, disables the entire device then you simply need a way to activate it.
Radio.
Design a circuit, or better something that appears to be a capacitor and functions as a capacitor but has a small internal compartment at say the top so that it performs at less than what it is rated for but has a small circuit that over-volts via a joule thief and causes a failure. Have the trigger be a small receiver that activates at a certain frequency probably in the ELF or SLF range with just a few bits needed as the activation key.
Put that into the supply chain of whatever industry and when you want to disrupt to cause economic damage, or even as part of causing a bit of chaos preceding a military attack, fire up your ELF station and start pumping out the few bits of data to activate.
ELF will penetrate hundreds of meters of water, it should reach inside most buildings and even if you only had something like a 5% success rate you'd disable a LOT of whatever you'd installed them in. If it's networking hardware, you could likely cripple anything that relies on the internet by causing considerable distributed failures.
I don't know about anyone else, but I did not like your comment because it mixes up tons of technical and high-level detail and also does so in incredibly long form.
You could have reduced the idea to "instead of embedding microchips in other microchips, why not make a device that simply allows one to disable the device remotely? Surely the size requirements would be much smaller"
Instead you go semi-technical about something you know semi-nothing about.
Only problem with LF stuff is that you need a pretty big antenna. You would be better off designing a chip with an RF section that operates in the GHz range so you can get away with a tiny microstrip antenna or with the antenna inside the chip.
I will admit radio is not my thing, that works too though and then you can make it a much larger activation key, even just bytes instead of bits would exponentially increase odds of not having an accidental activation which should make it not get set off by a router or microwave and you could probably activate it simply by flying over with a slightly modified cargo or passenger aircraft that looks business as normal but just belches high-power bursts of the activation signal.
Care to actually point out a flaw instead of replying with a low-value comment that serves no purpose other than stroking your own ego?
Yes, another user has already established ELF would be bad. Microwave would work completely fine however.
A 34.9 mm x 9 mm strip antenna would work more than adequately. Transmission from a geostationary satellite, or better a passing aircraft, could penetrate most non-metal structures (at least into the outer rooms) and would work.
You could easily fit the entire circuit into capacitors used in many power supplies, taking out a power supply is enough to take out hardware long enough to begin an attack (especially if combined with digital attacks on the grid and other critical infrastructure) or to simply cause some sort of economic damages.
And actually, there's a certain type of Atari power brick that is prone to destroying Atari computers as they are highly prone to failure which causes excess voltage being pumped into the machine as the last act of the power supply. The dreaded 'ingot' power supply (part number C061982). Do you know how many people open up wall warts/power bricks? Basically zero and many are actually un-serviceable as they are epoxied shut.
Radio.
Design a circuit, or better something that appears to be a capacitor and functions as a capacitor but has a small internal compartment at say the top so that it performs at less than what it is rated for but has a small circuit that over-volts via a joule thief and causes a failure. Have the trigger be a small receiver that activates at a certain frequency probably in the ELF or SLF range with just a few bits needed as the activation key.
Put that into the supply chain of whatever industry and when you want to disrupt to cause economic damage, or even as part of causing a bit of chaos preceding a military attack, fire up your ELF station and start pumping out the few bits of data to activate.
ELF will penetrate hundreds of meters of water, it should reach inside most buildings and even if you only had something like a 5% success rate you'd disable a LOT of whatever you'd installed them in. If it's networking hardware, you could likely cripple anything that relies on the internet by causing considerable distributed failures.