Never trust a chip you didn't fab yourself. This is seriously clever work. Bribe the right people at TSMC, and all of Apple's chips have a built-in side channel vector. Or any other fabless organization.

This might be a silly question, but even if you do fab it 'yourself', does that solve the problem? It might make it harder, but people can still be bribed, or have other pressures applied to them.

Would you put a back door in your own chip? I am not sure how bribe would work if your the target.

I suspect that you're thinking of bribing an organization. You're correct, it's hard to bribe an organization to act against its own interest. But instead, think about bribing one or two workers individuals within the organization. That's much more doable.