Steganography

Steganography conceals a message within an ordinary-looking carrier, such as an image, text, or audio file, so the message’s presence is not apparent.

Cover object: An ordinary file or physical object used to conceal a message. It provides the apparently innocent carrier in which steganographic data is hidden.
Image steganography: Steganography that embeds secret data in digital images. Images offer many pixel values that can be altered subtly to carry a payload.
Histiaeus: A Greek ruler of Miletus associated with an ancient account of a message hidden beneath a slave’s hair. Herodotus’s story is an early example of concealing a message on a human carrier.
Cryptography: The study and practice of protecting information by transforming it so unauthorized parties cannot understand it. Cryptography obscures a message’s meaning; steganography aims to obscure that a message exists.
Steganographic algorithm: A procedure for embedding secret data in a carrier and later extracting it. It determines how a message is inserted and recovered without obvious changes.
Audio steganography: Steganography that conceals data within digital audio signals. Audio methods exploit signal features that listeners may not notice.
Invisible ink: A substance used to write text that is not visible until treated or observed under suitable conditions. It conceals a message’s visibility, though the writing surface itself may still invite suspicion.
Encryption: The transformation of readable information into ciphertext using an algorithm and key. Encrypted data can be visible as a message even when its contents are unreadable.
Least significant bit: The rightmost bit in a binary number, representing the smallest place value. Changing selected pixel bits can encode data while altering image values only slightly.
Text steganography: Steganography that hides data in written or digital text. Spacing, formatting, and linguistic choices can serve as less obvious carriers.

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