"If" is the question, not "how long". And I think we'd stand a pretty good chance of handling a proof object in a secure way, assuming we have a secure digital transmission channel etc.

But the original scope of the thought experiment was assuming that we want to verify the proof. Wei Dai said:

Surely most humans would be too dumb to understand such a proof? And even if you could understand it, how does the AI convince you that it doesn't contain a deliberate flaw that you aren't smart enough to find? Or even better, you can just refuse to look at the proof.

I was responding to the first question, exclusively disjoint from the others. If your point is that we shouldn't attempt to verify an AI's precommitment proof, I agree.