What are the four-letter words that describe a job well done in confidentiality?

Shut up like a bottle: keep silent. Refers to speaking cautiously and keeping secrets strictly.

Keep secrets strictly and refuse to reveal them.

Secret but not leaked: leak. Keep secrets strictly and refuse to reveal them.

Keep secret: make it public. Keep a secret and refuse to announce it publicly

Keep a secret and refuse to announce it publicly: Speak openly. Keep it a secret and refuse to announce it.

Keep secrets strictly and refuse to reveal them. Same as "secret but not revealed".

You know and I know that only you and I know this secret and cannot tell others.

Clamp-mouth pliers: Same as "pliers", used to clamp something. Keep silent. Describes keeping secrets.

The secret delivery of a letter in a box is a secret delivery of a letter.

The submarine division attacks the distant submarine division: secretly mobilizes troops. Send troops secretly to attack distant enemies.

Tight-lipped: keep your mouth shut and don’t speak. Keeping your mouth shut is like having the top of a bottle tightly corked. Describes someone who speaks cautiously and keeps secrets strictly.

Retreat and hide in a secret place, hiding in a secret place without revealing your whereabouts. It is said that philosophy is subtle and profound and inclusive of all things.

Private clothing in private: civilian clothing. Private trip: traveling secretly. It used to mean that the emperor or officials put on civilian clothes and went secretly to the people to visit people's affairs or difficult and serious cases.

Chue Mei: hold it in your mouth; Mei: something like chopsticks with straps at both ends that can be tied around the neck; Ji Bao: walk quickly. Describes a secret rapid march at night.

Heirloom recipes refer to secret recipes passed down from ancestors.

Hidden by day and night: hiding; walking: on the road. Hide during the day and travel at night. Refers to covert activities taken to avoid being discovered by the enemy.