Steganography /(stĕg`ȧ*nŏg"rȧ*fy̆)/

Steg·a·nog·ra·phy

Steganography

n.
  1. The art of writing in cipher, or in characters which are not intelligible except to persons who have the key; cryptography.
  2. The branch of cryptography in which messages are hidden inside other messages; -- used commonly for the process of hiding messages inside a computerized image file, as for example hiding the name and copyright notice of the owner of an image as protection against violation of the copyright.