Introduction

Steganography is the science and art of hiding the presence of communication by embedding secret content into a cover document.
Unlike cryptography, steganography attempts to be not only confidential, but it aims to achieve secret communication.

Historically, hidden tattoos and invisible ink.
Computer and network technologies provide easy to use communication channels.

Steganographic systems use a cover medium to embed a hidden message.
A holiday picture may be used as cover medium.

Its invasive nature may leave detectable traces in the characteristic of the stego medium.