Yes, they are authentic. Titled players have to prove that they are who they are, and chess.com gives them their title and free diamond membership for life.
Chess Titles

Did you know that Jamaica awards the "National Master" title? It really does.
I wonder if the kind of chess skill possessed by a Jamaican National Master is about the same as the skill possessed by the Jamaican Bobsled Team?
Given that anyone can whip out a chessboard and set of pieces anywhere (it's even been done in the North Pole and in outer space) that failed joke holds no merit since Jamaica is a member of FIDE [through The Jamaica Chess Federation.]
I think the valid point is, how good is a national master from a small, predominantly poor, country in which not many people play chess?
I'm not knocking Jamaica per se, I see Jamaica is competing in the Winter Olympics right at this moment, which is awesome.
http://ratings.fide.com/topfed.phtml?country=JAM
Jamaica chess federation has a total of 63 active players.
http://ratings.fide.com/avgtoplist.phtml?country=JAM

A couple of years ago there was a similar thread on the easiest way to become a titled player and I believe the steps were: Become rich, move to a small impoverished nation, bribe the heck out of everyone you play, and become titled. You're not going to become an IM or Gm where norms are required but CM/NM, maybe even FM seems doable. I'm not saying that happens a lot (and it wasn't my post anyway) but it does seem more possible than somewhere with a lot of tournament players.
Are the chess titles given out here on Chess.com authentic/real?