I assume they were referring to TEMPEST. Basically every piece of electronic equipment has unintentional radiation. It's super-easy to read keyboard input even from a wired keyboard, or to read from a screen (CRT or LCD) based on the pattern, with about $50k (in 1999) of RF equipment -- could do it in the hundreds or thousands now.
Reading from a CPU is harder, but it can be done, especially if you only need to recover one thing (like a key), can force the processor to load the key on demand (like, sending a packet which needs to be decrypted), can record a lot of samples, and know the structure of the software and equipment which is processing it (like if it is a standard phone). Cryptography Research (Paul Kocher, aka one of the smartest people in security who doesn't work at NSA) and his team have done this for years -- live demo of the attack in ~10 minutes at various conferences.
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I assume they were referring to TEMPEST. Basically every piece of electronic equipment has unintentional radiation. It's super-easy to read keyboard input even from a wired keyboard, or to read from a screen (CRT or LCD) based on the pattern, with about $50k (in 1999) of RF equipment -- could do it in the hundreds or thousands now.
Reading from a CPU is harder, but it can be done, especially if you only need to recover one thing (like a key), can force the processor to load the key on demand (like, sending a packet which needs to be decrypted), can record a lot of samples, and know the structure of the software and equipment which is processing it (like if it is a standard phone). Cryptography Research (Paul Kocher, aka one of the smartest people in security who doesn't work at NSA) and his team have done this for years -- live demo of the attack in ~10 minutes at various conferences.