you can't prevent encryption. There is no barrier to entry to people writing encryption from scratch. You could even do it with a combination of computer and

you can't prevent encryption. There is no barrier to entry to people writing encryption from scratch. You could even do it with a combination of computer and paPer, if you don't trust the computer... People using 3rd party closed source encryption tools don't really have a reasonable expectation of non-backdoored software.