In his testimony, Comey will claim — as he has repeatedly over the last 18 months — that wide-scale public adoption of encryption technology will cripple the FBI's ability to find and catch terrorists. The public record to date shows otherwise.

Last year, Comey blasted Apple and Google for moving to make their own products more secure by cleaning up existing software vulnerabilities and, in Apple's case, implementing end-to-end encryption for its iMessage instant messaging app and Facetime video chat app.

In May 2015, Comey again attacked technology companies and civil liberties groups for sending a letter to President Obama calling for a halt to executive branch efforts to compromise private sector encryption standards and products.

"I read this letter and I think that these folks don't see what I see, or they're not fair minded," Comey said.