Ham radio anon here. You could use something like FreeDV with symmetric crypto and a nonce for every frame. FreeDV works even when you can't hear the signal, down to around -10 dB SNR in a 2.5 kHz bandwidth. This is better than SSB.
Codewords can work just as well as encryption, and works over analog radio (FM, SSB).
You can use APRS for simple data communication and station-to-station chat.
Keep in mind even if you use encryption the feds can easily use HFDF to pinpoint your location. Consider using a remote controlled rig.
Using very large bandwidth can also work to avoid HFDF, since that spreads your signal out enough for it to just look like noise. Something like CDMA and UWB combined.
You can get very large coverage per Watt if you use HF bands like 20m (14 MHz) or 40m (7 MHz).