The self-portrait's hidden secret was revealed after the collector took the painting to his local hospital, on the advice of an art expert.

That's the little hidden secret: the quest for more doesn't really have a finish line.

There isn't any hidden secret to a long relationship.

She then presents a chart with a set of hidden secret ingredients on the top row, and hidden food groups on the left column.

From these pieces of information the adversary can attempt to recover the hidden secret key used for decryption.