You can trust a chip to correctly do cryptographic computations by comparing with another, more trusted system (an FPGA, if you want to go to absurd lengths).
You can protect yourself against faulty key generation by generating the key offsite or on a HSM.
However, a flaw in a RNG that allows a third party (hello NSA) to break cryptography - you cannot defend from that, you can't even detect it.
> However, a flaw in a RNG that allows a third party (hello NSA) to break cryptography - you cannot defend from that, you can't even detect it.
You always put bad randomness through enough calls of one way functions that reversing them is computationally infeasible for your adversary for the lifetime of the secret.
You can protect yourself against faulty key generation by generating the key offsite or on a HSM.
However, a flaw in a RNG that allows a third party (hello NSA) to break cryptography - you cannot defend from that, you can't even detect it.