to keep one's counsel/to keep or hold your cards close to your chest

What is the Greek equivalent expression to the above? Examples of use:-
keep/hold your cards close to your chest
--You never quite know what Barry's going to do next - he keeps his cards very close to his chest.
For 'to keep one's counsel, see:-https://en.m.wiktionary.org/wiki/keep_one%27s_counsel. ;)

Τα πρώτα που μου έρχονται στο μυαλό:
Είναι κρυψίνους / Είναι σφίγγα / Δεν ανοίγει τα χαρτιά του

Ευχ, Θέμι.