Well, I read the entire article, and it's quite interesting that there are things like Keyczar and cryptlib out there, I still think it's a poor example. Other than a brief note on encryption does not equal authentication, they never touched on the fact that encrypting the cookie data itself isn't a real solution, as the encrypted cookie can be sniffed, and replayed to the server.

So, while standard user can't hack their own cookie for escalation, they can sniff admin cookies to get that escalation. If the cookie is used for authentication or authorization, encrypting it's content is providing a false sense of security, no matter what nifty library you choose or not choose to do it with.