nice paper from:Hal Berghel, David Hoelzer, Michael Sthultz

Digital data hiding is actually a cluster-concept that spans many
contexts. In modern times, non-physical data hiding is usually
associated with digital forms such as cryptography, steganography, and
watermarking. Although related in the sense that they all are means to
achieve secure or proprietary communications, there are differences
among their three activities at a number of levels – some of which are
quite subtle. To illustrate, the cryptographer’s interest is primarily
with obscuring the content of a message, but not the communication of
the message. The steganographer, on the other hand is concerned with
hiding the very communication of the message, while the digital
watermarker attempts to add sufficient metadata to a message to
establish ownership, provenance, source, etc. Cryptography and
steganography share the feature that the object of interest is
embedded, hidden or obscured, whereas the object of interest in
watermarking is the host or carrier which is being protected by the
object that is embedded, hidden or obscured. Further, watermarking and
steganography may be used with or without cryptography; and
imperceptible watermarking shares functionality with steganography,
whereas perceptible watermarking does not. Overviews exist for
cryptography [13], steganography [9], [14], and watermarking [3].

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