There are no technical solutions to human problems. This has been explained over and over again, most famously in Randall Munro's XKCD comic where the secret police resort to hitting someone with a $5 wrench until they give up the password.

If you're in a repressive state and you're worried about your data being exfiltrated the best security practice of all is not to create records of illegal activity. If you have to store such material, don't keep it on a communications device, put it on an external storage device, hide it somewhere outside your home, and don't tell anyone about it.