Student or Learner
Word to describe or call someone who doesn't like to reveal details about himself or things he knows that may be deemed advantageous in current state of affairs. So that be does not lose his own potential advantage.
You could say "He keeps his cards close to his chest".
Remember - if you don't use correct capitalisation, punctuation and spacing, anything you write will be incorrect.
Thanks for the replies, they've been helpful, although I don't see how shrewd fits the description.
I'm looking more for a singular descriptive word to call the person, the closest word I can think of is an "expedient".
Can you actually call someone an expedient?
Both but preferably a noun.
We are not infrequently asked here for words, expressions or idioms for certain ideas. Very often, English simply does not have them. There is no reason why we should have one word for someone who doesn't like to reveal details about himself or things he knows that may be deemed advantageous in current state of affairs. So that he does not lose his own potential advantage. That's quite a few ideas to pack into one word.
Occasionally, we can use the name of a real person or fictional, if that person happens to embody certain characteristics known to many people - there are, for example, 24 citations with the adjective 'Chaplinesque' in COCA, and most of us know what 'malapropisms' are. If you wanted to describe someone who was handsome, intelligent, charming, generous, who was very knowedgeable about English grammar, and who was a patient, caring, inspirational teacher, you might say he was a 5jj.
Then again, you might not.