I still don't get it. I mean - when you're talking about power supplies, there are welding power supplies that are light. A power supply is lighter by default these days because they can be made with mosfets instead of big, heavy transformers.

As for hardware cryptography modules - again - you can buy an ARM chip that's the size of your thumbnail that's basically a full blown computer.

I'd be interested to look at the insides of one. I wouldn't be surprised if making them EMP hardened would be a big component of where the bulk comes from.