From Tension Software:
Private Contact is a native Cocoa software to manage on macintosh an address book with reserved data inside.
In this way, informations inside documents, relative to various persons, can be read only by the Macintosh owner, and in case of unauthorized access or theft of the Mac, the data inside Private Contact documents can't be read.
Private Contact is easy to use. Open and closing operations are absolutely easy and similar to the one of standard Mac OS X application plus just a password to provide every time the user opens a document.
Private Contact uses the powerful Blowfish algorithm, to encrypt data. The use of the blowfish algorithm, managed at decoding level by Apple native libraries available on any Mac, allows to work in a reliable way.
Also in the unfortunate situation your Mac come in the hands of expert hacker, without the document password, they can't be able to read data inside the document because are all Blowfish encrypted.