(excerpt)
Rep. Trey Gowdy attempts to question FBI director James Comey about how many people have the power to 'unmask' the name of a U.S. citizen in communications intercepted by the intelligence services. This information would serve as the basis for any investigation into who has been leaking classified documents.
(video at link)
Only those persons or agencies who collect surveillance have the authority to unmask U.S. Citizens.
GOWDY: Did you brief President Obama on -- well, I'll just ask you. Did you brief President Obama on any calls involving Michael Flynn?
COMEY: I'm not gonna get into either that particular case that matter, or any conversations I had with the president. So I can't answer that.
...didn't make it into the video.
Obama issued an EO to expand access to unmask Americans. That is how his UN Ambassador was able to request hundreds unmaskings.