cagey

adjective. very cautious or wary (e.g. of revealing important information)

Like the Thanksgiving holiday, "cagey" was Made in USA.

"Some people are cagey about using Facebook for work contacts"
"Politicians are often cagey when they're asked difficult questions by reporters, and parents can get equally cagey when their kids start to ask questions about how exactly Santa Claus fits down the chimney."

http://www.vocabulary.com/dictionary/cagy