> If NSA and only NSA can crack a particular system, they probably wouldn't mind using it for their own secrets.
How do you think they could assess that they, and only they will ever be able to exploit a particular cryptographic vulnerability at any time over the next few decades?
They can’t, they would be well aware of that, and they are extremely risk averse.
> And anyway why is there any reason to believe they really do use the system they say they use?
Because these systems exist widely throughout government today.
And anyway why is there any reason to believe they really do use the system they say they use?