Microcontroller Exploits

24  Clipper Chip Diffusion ROM

In the Nineties, the Clinton administration had an obsession with key escrow cryptography. They wanted to provide American citizens with cryptography that the US government itself could break, but in a way that excluded foreign governments from the same privilege. This was called the Clipper chip in general, and in this chapter we’ll focus on the PCMCIA generation of that chip, known as the MYK82 or Fortezza card. We’ll dump its firmware and extract it into useful bits.

It worked roughly like this: suppose that Monica calls Bill for a private conversation. As she hits the encrypt button, the two telephones perform a key exchange. After the keys are exchanged, her phone will send Bill’s phone a bundle called the ...