When Michael Chertoff made the case against back doors, he noted that if the government moved to require back doors, it would leave just the bad guys with encrypted communications.
The second thing is that the really bad people are going to find apps and tools that are going to allow them to encrypt everything without a back door. These apps are multiplying all the time. The idea that you’re going to be able to stop this, particularly given the global environment, I think is a pipe dream. So what would wind up happening is people who are legitimate actors will be taking somewhat less secure communications and the bad guys will still not be able to be decrypted.