[bombcar]

IIRC there is at least one known case where a moderately major criminal was let go rather than the government disclosing how they got the evidence on him. The assumption has been that they had a way of compromising TOR that they didn't want to reveal.

[generalizations]

One implication of that - make sure there's no available means of parallel construction, and it's ok if they catch you in some way they don't want to reveal. As long as you're not valuable enough, that is.

[bombcar]

That's the real bar for any security, really - make it so it's not worth the while of people who could defeat it.

Because eventually, no matter what you do, if you're up against a nation state, they'll just make you dead.