I’ve just been pointer to this jaw-dropping paper: “Stealthy Dopant-Level Hardware Trojans” that shows how a complex integrated circuit could be maliciously compromised.
This new type of sub-transistor level hardware Trojan that only requires modication of the dopant masks. No additional transistors or gates are added and no other layout mask needs to be modied.
Since only changes to the metal, polysilicion or active area can be reliably detected with optical inspection, this dopant Trojans are immune to optical inspection, one of the most important Trojan detection mechanisms.
As proof of concept they were able to make changes to several hundred gates of an Intel Ivy Bridge processor which sabotaged the Random Number Generator (RNG) instructions. The exploit works by reducing the amount of entropy the RNG normally uses, from 128 bits to 32 bits. Any cryptographic keys generated by the compromised chip would be easy to crack. The hacked RNG was not detected by any of the “Built-In Self-Tests” mandated by the National Institute of Standards and Technology.
All in all, it doesn’t matter how strong your cryptography method is, it can be easily cracked if you don’t have a reliable source of entropy, and in this case, it seems somebody has cut to the root of the “problem”. Be aware.