33C3: Chris Gerlinsky Cracks Pay TV


People who have incredible competence in a wide range of fields are rare, and it can appear deceptively simple when they present their work. [Chris Gerlinksy]’s talk on breaking the encryption used on satellite and cable pay TV set-top boxes was like that. (Download the slides, as PDF.) The end result of his work is that he gets to watch anything on pay TV, but getting to watch free wrestling matches is hardly the point of an epic hack like this.

The talk spans hardware reverse engineering of the set-top box itself, chip decapping, visual ROM recovery, software reverse analysis, chip glitching, creation of custom glitching hardware, several levels of crypto, and a lot of very educated guessing. Along the way, you’ll learn everything there is to know about how broadcast streams are encrypted and delivered. Watch this talk now.

Some of the coolest bits:

  • Reading out the masked ROM from looking at it with a microscope never fails to amaze us.
  • A custom chip-glitcher rig was built, and is shown in a few iterations, finally ending up in a “fancy” project box. But it’s the kind of thing you could build at home: a microcontroller controlling a switch on a breadboard.
  • The encoder chip stores its memory in RAM: [Chris] uses a beautiful home-brew method of desoldering the power pins, connecting them up to a battery, and desoldering the chip from the board for further analysis.
  • The chip runs entirely in RAM, forcing [Chris] to re-glitch the chip and insert his payload code every time it resets. And it resets a lot, because the designers added reset vectors between the bytes of the desired keys. Very sneaky.
  • All of this was done by sacrificing only one truckload of set-top boxes.

Our jaw dropped repeatedly during this presentation. Go watch it now.



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