Essentially, steganography is the art of concealing private or sensitive information within a carrier that for all intents and purposes, appears innocuous. steganography relies on the sender and receiver agreeing upon the method by which the information will be and therefore some means of prior communication is essential for steganography to be of any use. The science of concealing information was later to be known as “steganography” and the current technology of “Digital Watermarking” has taken its root from it. The term “watermark” in terms of digital data was taken from the concept of watermarks used to prevent faking of currency notes. Steganography is sometimes confused with cryptography. Although the two can co-exist as discussed later in this document, they are not the same. Both are used to protect information but steganography is concerned with concealing information thereby making it unseen while cryptography is concerned with encrypting information thereby making it unreadable. Different categories of Steganography.
Almost all digital file formats can be used for steganography, but the formats that are more suitable are those with a high degree of redundancy. Redundancy can be defined as the bits of an object that provide accuracy far greater than necessary for the object’s use and display. The redundant bits of an object are those bits that can be altered without the alteration being detected easily.
Image and audio files especially comply with this requirement, while research has also uncovered other file formats that can be used for information hiding. The figure below shows four main categories of file formats that can be used for steganography.
Department of Computer Engineering
Sardar Patel Institute of Technology