Everyone guesses he's a tester. Or a super-secret-spy-type guy.
In the first case, the xboxes make sense as a testing tool, but the knowledge of cryptology does not. And "being able to get a job anywhere" does not fit the job profile.
In the latter, the knowledge makes sense, but the xboxes are a stretch. Again, being basically guaranteed a job does not fit the job profile.
I'm more inclined to think programmer/developer. "Eggheads", as they have previously been called in this thread, are in high demand, to develop new hardware, and software, and find new applications for existing foundations. I know Microsoft likes to keep all the best and worst information about new xbox games locked up as tightly as possible and only allow what they want to show off to leak before release. Going so far as to make advertisements with absolutely no game-play or cutscenes in them - most of what they do show is climatic events from a different viewpoint, or things about the world, using a completely different cinematography method then the game (I'm pretty certain they do this, but not 100% sure). They even try their best to keep the companies working on games for them from leaking any info before release.
That would certainly explain the security. And the xboxes. And the cockiness of being able to land any job he wants. And if he's a developer, whether hardware or software or both, he's most certainly had some experience with various forms of programming, including encryption. So being a developer makes a lot of sense.
And if he's not able to call enough shots to bring in some other entertainment, he's certainly not management or a project head. So I'd say he was hired to figure out how to do things, not dream up new things for others to figure out. So he's a doer, not a dreamer, but definitely skilled.