Steganography-Uses

Steganography is the secret transmission of a message. It is distinct from encryption, because the goal of encryption is to make a message difficult to read while the goal of steganography is to make a message altogether invisible. A steganographic message may also be an encrypted as an extra barrier to interception, but need not be. Steganography has the advantage that even a talented code-cracker cannot decipher a message without knowing it is there.

Like most other forms of cryptography and secret writing, steganography has thrived in the digital era. Most digital documents contain useless or insignificant areas of data, or involve enough redundancy that some of their information can be altered without obvious effect. For instance, one might conceal a message bitstream inside a digital audio file by replacing the least-significant bit of every waveform sample -or every n th waveform sample with a message bit; the only effect on the file, if played back as audio, would be a slight decrease in the sound quality -probably imperceptible. Although steganographic messages can be hidden in any kind of digital files, image files, because they contain so much data to begin with, are usually used for digital steganography. Today a number of commercial or shareware programs exist for encoding text into steganographic images , and are used by millions of people worldwide who wish to evade surveillance, especially by governments. This includes people who have reason to fear punishment for expressing their political ideas, as well as terrorists.

Steganography is also used for the less dramatic purpose of watermarking , which is the hiding of information indicating ownership or origin inside a digital file. Physical watermarking, the practice after which digital watermarking is named, is the impression of a subtle pattern on paper using water. A watermark is only visible when the paper is held up to a light. Watermarking can be used for digital authentication -i.e., to prove that certain party was indeed the source of a file or to check whether a digital file was obtained in violation of copyright.