Start with the simple bomb… a timer controls applying power to the blasting cap embedded in the C4 or fertilizer-diesel mixture or whatever.
Pull the cap out, the major explosive does not receive an immediate enough powerful shock, does not explode.
So what are you as a bomb-maker going to do to prevent this?
Hiding the bomb is a good start.
IIRC the Mad Bomber in Boston, if I remember long ago articles, used a mercury switch to detect if the bomb was being moved - once armed, jarring or tilting the bomb could close the circuit using a tiny glass vial with a blob of mercury and two wires in it. Nowadays, there are electronic gizmos t detect movement, but same idea.
But then, the bomb has to avoid vibration after being armed (powered on). Those Speed movies where the bomb can be shaken around by hitting LA potholes at 60MPH but you still can’t pick it up - pure pig leavings.
Then of course, build a dam around the bomb (Clay?) and pour in liquid nitrogen. That should freeze any mercury fuses, and as a bonus kill any battery.
So, you Mr. Bombmaker add a temperature switch to the bomb. Too cold, it burns up.
Put a switch on the lid, if the bomb box is opened, boom. A simple variation on tripwire, weight sensitive switch under carpet, etc.
Pull the blasting cap out? Make a fake blasting cap that is actually a spring-loaded switch - pull it out, the circuit closes, mission accomplished. So if the bomb has 2 blasting caps, is that insurance or a trick? But, how good are your mimicry skills in making fake blasting caps? Instead of pulling it out, slowly peel back the C4?
Does the wiring sense when a wire has been cut? does the wiring sense changes to capacitance as the wires are handled or the insulation is cut and the wire clippers are about to do their thing? Dual ignitions that will trigger if their buddy goes offline, to prevent tampering You better have a pretty sophisticated bombmaker who knows real fancy electronics…
Plus, there’s the Rube Goldberg principle - the more complex the device, the better the odds it won’t work. Remember in the second wave of Tube bombings in London (and the underwear bomber), the terrorists could not even make explosive that went “bang” instead of “fizz”. Hooking a cellphone to a blasting cap trigger seems to be the limit of modern tech tricks. (Leading to the result that when they tried to blow up the president of Pakistan over 10 years ago, the bridge blew up a minute after his car went over it - presumably the trigger text arrived after his jammers were out of range…)
But basically, your typical bomb is built ot meet the needs it expects to encounter. How tamper-proof and analysis proof does it have to be?