The article you cite states exactly my prior point. It attributes to "a CIA Official" -- who is that? If the CIA is making a formal statement, don't they have a formal spokesman?
And also note that "they aren't certain"? So either this is an identification or it isn't. I say that your article is NOT an identification.
How would he prove he's alive? Grant an interview to Dan Rather; appear in a credible video with today's NY Times on the table. Come on -- kidnappers have been 'proving' the existence of hostages for years.