The big problem there is not that he does it, but that it can be done. You can't be sure if someone else (i.e. some intelligence agencies) know it already, and

The big problem there is not that he does it, but that it can be done. You can't be sure if someone else (i.e. some intelligence agencies) know it already, and is actively breaking encryption, even if he doesn't. Your encryption is by definition not safe, and everyone should change it. Unless, of course, it requires magical/unachievable technology like some impossible yet quantum computer or hundreds of years.