He said, "I know a lot about hacking. And hacking is a very hard thing to prove. So it could be somebody else. And I also know things that other people don't know, and so they cannot be sure of the situation."
He also added that computers are a risky form of communication.
"It's very important, if you have something really important, write it out and have it delivered by courier, the old fashioned way because I'll tell you what, no computer is safe," Mr. Trump added. "I don't care what they say, no computer is safe. I have a boy who's 10 years old, he can do anything with a computer. You want something to really go without detection, write it out and have it sent by courier."