SPOILER of Batman Arkham Origins and "Batman Series" in general.
Those who don't want to get spoiled then please don't click. The identity of "Black Mask" is given here. Again don't click if you don't want to get spoiled. Dont blame me if you click.
http://i.imgur.com/OEdXwlB.jpg
Source: http://www.neogaf.com/forum/showthread.php?t=701806