Tamper-evidence (which itself might be served by open and auditable HW and codes) would probably be a more robust and readily tested option. I can think of how

Tamper-evidence (which itself might be served by open and auditable HW and codes) would probably be a more robust and readily tested option. I can think of how that could be applied to SW, and possibly chip designs themselves. Overall hardware kits somewhat less so. E.g., a "resistor" or "capacitor" with its own CPU and potentially some weaponised capability could probably avoid detection from such methods. Installing an entire secondary circuit board (as seems to have been the case for the AR924 pagers used on 17 September) should be more immediately detectable, though a partial tear-down would be required. As for in-house production: there's been a greatly increased reliance on "COTS" (common off-the-shelf) products in many realms, including the military: "Off-the-Shelf Solutions for the Battlefield" (2008) How are commercial off-the-shelf products helping to drive down the military's costs? Steve Polak and Brendan Jordan discover how these products are helping coalition forces in their fight for interoperability. ... Since the 1970s the steady shift towards a consumer-based society and economy has seen civilian commercial entities increasingly replace traditional military suppliers as the leading drivers in technological advance. In no industrial sector is this more apparent than in electronics, where the once dominant technological edge of military electronics of the 1960s has been replaced with the increasingly cutting-edge nature of civilian microelectronics driven by insatiable consumer demand. <https://www.army-technology.com/features/feature1918/ https://www.army-technology.com/features/feature1918/> More generally (Wikipedia): <https://en.wikipedia.org/wiki/Commercial_off-the-shelf https://en.wikipedia.org/wiki/Commercial_off-the-shelf>