steganography

n. [ Gr. stegano`s covered (fr. ste`gein to cover closely) + -graphy. ] 1. The art of writing in cipher, or in characters which are not intelligible except to persons who have the key; cryptography. [ 1913 Webster ]

2. Specifically: 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. [ PJC ]