stegography

Stegography, often confused with steganography, is the practice of concealing a secret message within another non-secret medium so that the existence of the message is not detectable. The standard term is steganography, derived from Greek steganos “covered” and graphein “to write,” and it refers to hiding information rather than merely encrypting it.

Carriers include digital media such as images, audio, video, and text, as well as non-digital media like microdots or invisible ink. Techniques range from embedding data in the least significant bits of image pixels to transform-domain methods that spread the payload across a signal, and to digital watermarking that is designed to survive processing. Hidden data can also reside in metadata or in the structure of a file.

Historically, steganography dates to ancient practices such as concealing messages in wax tablets, tattooed or shaved heads, or folded notes, evolving to modern digital methods that exploit media redundancy. The field of steganalysis studies methods to detect and extract hidden information and to identify the carriers and techniques used.

Steganography differs from cryptography: cryptography hides the content of a message, while steganography hides the existence of the communication. Its effectiveness depends on the cover medium’s tolerance to modification and on the resilience of the embedded payload to compression or editing.

Applications include copyright watermarking, covert communication in some contexts, and information hiding in digital media. Ethical and legal considerations apply, and steganography can be used for both legitimate and illicit purposes.