keep one's cards close to one's chest

Etymology
Because playing cards kept close to one's chest are difficult to see for an opposing player.

Verb

 * 1)  To avoid revealing one's thoughts, circumstances, or plans.

Translations

 * Finnish:, pitää korttinsa piilossa
 * French:
 * German: sich nicht in die Karten schauen lassen
 * Polish: nie odkrywać kart, nie odkryć kart
 * Spanish: no soltar prenda