https://www.theregister.co.uk/2018/07/27/screaming_channels_attack/

Side-channel radio attacks just got a whole lot worse: a group of researchers from Eurocom's Software and Systems Security Group has extracted crypto keys from the noise generated by ordinary communications chips.

Unlike more esoteric side-channels, which often need physical access to a target machine or some kind of malware implant, this leak comes from radio devices working as intended by the maker. If an SoC packs analogue and digital operations on the same die, the CPU's operations inevitably leak to the radio transmitter, and can be traced from a distance.