Secrecy is the badge of fraud. – Sir John Chadwick

To him that you tell your secret you resign your liberty. – Anon.

To have found you is a dear happiness; and to be Apollos son is beyond all my hopes; but there is something I want to say to you alone. Come; this is a private matter between us two – anything you tell me shall be as secret as the grave. – Euripides

To know that one has a secret is to know half the secret itself. – Henry Ward Beecher