The airwaves can be intercepted, sure, but that isn't what I mean. I've done quite a bit of work that involved ground processing of signals from government owne

The airwaves can be intercepted, sure, but that isn't what I mean. I've done quite a bit of work that involved ground processing of signals from government owned spacecraft and all of it was encrypted using pre-shared hardware keys, not PKI. Granted, that was military applications and maybe JPL and NASA don't have the same security requirements, but seemingly they should? Maybe the Mars rover is less of a desirable attack target for a nation state adversary than a spy satellite, but it is a pretty expensive project you would seemingly still want to protect as much as you can.