[jacquesm]

Just pass a DVD with white noise when you meet in person. That should keep you in one time pads as long as you want to communicate with someone. All you need is XOR and a bookmark. Of course you need to meet once, if that's not feasible you're going to get more technical.

[redler]

In Vernor Vinge's A Fire Upon the Deep I recall a plot element along these lines. Traders traffic in cubes of material that acts as a super dense source of pad data. Your communication partner on another ship would have the twin cube, and the two would be synced up and then provide the carrier data stream for video and other content. When your cubestuff is exhausted your secure authenticated comms cease.

[dheera]

If the censorship is based on the government being able to make some sense of what you're communicating, XORing with a PSK will not work, because they will see meaningless garbage and block it. The reason I suggested cat pictures is because the censors will see actual cat pictures and (hopefully) consider the protocol not worthy of blocking.

s/cat pictures/whatever you want/