alt Hacker NewsReally interesting concept! I would not have thought of EMR variation as a usable side channel for this.
IIUC, the EMR increases following scene changes (like a light being turned on or off) are a result of the fact that video codecs try hard to compress similar images. So, I speculate that an "extremely bad codec" that simply dumps raw pixels to storage would not produce such variation, and therefore remain undetectable?
Potentially, although raw pixel data presents its own challenges - one 1080p60 camera will fill a terabyte of storage in less than an hour.
A better mitigation might be to take a leaf from cryptography and develop a constant-time codec.