TEMPEST -- the NSA program addressing "compromising emanations," the electromagnetic leakage that lets a listener reconstruct what a device is processing without tapping a wire -- traces to a 1943 Bell Labs discovery and became a formal government concern once the CIA read plaintext from a quarter mile down a signal line in 1951. It's the operational-trust counterpart to the fabrication-trust question this site already covered in Trusted Foundry: not who built the chip, but whether the finished device leaks what it processes.