A technique used for secret communication between two parties, steganography is used to hide a secret message within another, so that the presence of the secret message cannot be easily discerned, yet its content can be revealed by the sender and the intended recipient.
The word steganography means covered writing in Greek. It is derived from the words "steganos," which means covered, and "graphia," meaning writing. In contrast to cryptography, which renders a visible message unintelligible to the unauthorized person, steganography hides the very existence of the message which may or may not be encrypted.
Advances in the fields of computer, communication, and signal processing have led to the discovery of sophisticated steganography techniques that can be used to embed various forms of information in various types of media. They can be used to conceal codes, text, audio, video, or graphics in digital images, audio, or video. The concealed information is usually unrelated to the cover media. Additionally, the covert message become unrecoverable, once the cover media leaves the digital domain or undergoes any digital manipulation or transformation.
Vs. Digital Watermarking
A related field to steganography is digital watermarking which has also been used to hide information in a variety of media like images, audio and video. Watermarking differs from steganography in the application of the technology and the algorithms used to embed the information. Instead of targeting secret communication, digital watermarking targets content identification to enable a wide range of applications that includes document track and trace, broadcast monitoring, device control, and linking the physical and digital worlds. Unlike in steganography, the embedded message in digital watermarking is usually related to the cover media, and its size is much smaller. Digital watermarking techniques also often focus on reducing the visibility of the embedded message, while maintaining excellent robustness to a variety of attacks. Although imperceptibility is not as critical a requirement for watermarking as it is for steganography, robustness is usually very crucial as the cover media is expected to go through some form of ordinary digital manipulation or analog-to-digital conversion. Sophisticated watermarking techniques have recently been developed, and they can be used to embed in printed text, graphics, or images as well as in digital images, graphics, audio, or video.
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