> sci-fi technology

You know, based on some people in China has learned building VPN/proxies, the best and cheap way to communicate under surveillance/censorship is to hide it in plain sight. In fact, that's how most these proxy software works.

So no, you don't need sci-fi technology. If you really want to communicate, context-coherent code words though bugged phone line should be enough, at least enough to arrange a meet up.

Also a interesting thought: maybe one day when human invented a device that could listen to quantum communications, we turn it on and ended up detecting a sea of encrypted conversations from another space-time perhaps even an universe just aligned with ours, and the device also experiences unexplained packet loss. That's what I call a plot of a sci-fi story :)