[Tichy]

A onetime pad would be a good example of something I would not like to have on me if got grabbed by some oppressive regime. That is the kind of problem I mean.

Tor is not a solution, because it could be found on your computer.

Radiowaves - I don't know, I would also expect them to be easily detectable, but I'll look it up.

[bwarp]

A one time pad can be easily hidden amongst other text i.e. a book printing with some rules applied (third letter of every alternate sentence).