Any reasonable HIDS/HWIDS, beyond physical PCB auditing, x-ray verification and supply-chain chain-of-custody documentation, needs to include continuous monitor

Any reasonable HIDS/HWIDS, beyond physical PCB auditing, x-ray verification and supply-chain chain-of-custody documentation, needs to include continuous monitoring firmware using end-to-end public key-verifiable signatures. Also, open-source hardware, including the firmware, would alleviate some of the downsides of closed blobs.