Reflections on Trusting Trust should be mandatory reading for all "criminals"?
Not only software is a problem, but the hardware too. If you want some strong guarantees about the system you are using, then you must make both hardware and software yourself. At the same time, you then cross your fingers that you have not introduced any bugs.
Maybe, using an old typewriter, paper and the post-office is becoming more secure than your computing platforms. I guess you should use some kind of code. But then, OTP has a very long history and is very secure. Oh, yes, the RTT is lower, but that is compensated with the better security.
But in the end, it will be the users who make simple or stupid mistakes that cause them to be caught. That cannot be fixed with any type of technology. Or, can you already get an integrated brain replacement?