[Cryptography] TV set power correlates to TV channel?

[Peter Gutmann]

Jerry Leichter <leichter at lrw.com> writes:

>Now move out to the point where you're seeing the power drawn by the whole
>house.  Yes, the signal will still be there - but whether you can pull it out
>from other junk on the line, and the distortions introduced by the house
>circuitry, is a difficult question to answer without trying it.

Having read papers in the past on power disaggregation, I would say it's going
to be quite tricky.  Sorting out whether you're running your kettle at the
same time as your microwave is one thing (very different power characteristics
overlaid), but determining precisely what your TV is doing is an entirely
differnt kettle (of fish, this time).  

This stuff is blind signal demodulation, starting with a fluctuating power
line signal you need to sort out that this bit there is probably a microwave
and that bit over there is most likely a kettle (some are very easy, for
example I can tell just by looking at the power monitoring graph whether the
hot water, fridge, and/or heatpump are running, they have very distinctive
line signals), but for TV programs you'd probably need far more precise
knowledge of the TV model, firmware rev, and details of any other devices with
SMPS that'll be injecting noise and causing fluctuations at the same time.

It's a matter of what's easiest.  The MIB can hack your smart meter and
covertly replace it with a far more powerful piece of gear that has what it
takes to sort out which TV program you're watching based on OLED light-pattern
power consumption, or they can point a $5 webcam at your window and record it
straight from the OLED source.

>Of course, you do get the question:  Why would anyone bother?

Yup, exactly.

Peter.