beijing okay

If say something malevolent or gossip about a person not present you can say:

天知地知你知我知 (tian1 zhi1 di4 zhi1 ni3 zhi1 wo3 zhi1)

The literal translation is "Heaven knows, earth knows, you know, I know." This implies that although there are four "people" present, it's unimportant because it'll be kept a secret.