This paper introduces steganography, the art and science of hidden writing. The purpose of steganography is to hide the existence of a secret message from a third party. The most popular modern application of steganography involves concealing messages within least significant bits of image or sound files. Another application of modern steganography is a steganographic file system. Steganography is also used by some modern printers, where tiny yellow dots that contain encoded printer serial numbers, as well as other information, are added to each printed page.
I chose modern steganography as a topic for my course paper primarily because I have had an interest in the topic before, and would like to use this paper as an opportunity to expand my knowledge of steganographic techniques, especially in their modern applications. Introduction
Steganography is the art and science of hidden writing. The purpose of steganography is to hide the existence of a secret communication from a third party. Usually, a steganographic message will appear to be something else: a picture, an audio file, or some other message (the covertext). The advantage of steganography over cryptography alone is that steganographic message does not attract attention to communicating parties. An apparent encrypted message, no matter how unbreakable it is, can arouse suspicion and may in itself be incriminating. If suspicion is raised, then the goal of steganography is defeated. Since there is always a possibility that secret communication will be uncovered, steganography is often used together with cryptography. A steganographic message (the plaintext) is first encrypted by some modern encryption algorithms, and then a covertext is modified in some way to contain the encrypted message (the ciphertext), resulting in stegotext.
A typical digital steganographic encoder is presented on Figure 1. The message is the data that the sender wishes to remain