Ciphers as well as codes are transmitted openly. Everyone can see that they exist. Not so with steganograms.
Steganography is the art and science of communicating in a way which hides the existence of the secret part in that communication. During the Italian Renaissance and the time of the Elizabethan Age in England cryptography was very popular, for political reasons as well as for amusements (see John Dee).
In literature steganography played an important role. Many steganographs of that period have only been deciphered recently like some of the Shakespearean sonnets, which now seem to proof that the actor William Shakespeare was not the author of the famous poems and dramas, but that the latter' name was, and Francis Bacon, or even Francis Tudor, as some ciphers and other sources talk of him as Queen Elisabeth I.'s secret son.
for further details see:
One kind of steganogram is digital watermarking:
Watermarks protect digital images, videos, but also audio and multimedia products. They are made out of digital signals, put into other digital signals. They try to be invisible on first sight and should be nearly impossible to remove. The process of producing watermarks is to overlay some sort of identifying image over the original image (non-digital watermarks, like on money can be seen by holding the paper against light). Copying the image destroys the watermark, which cannot be copied. Any alteration of the original destroys the watermark, too.
Watermarking is one of the typical inventions of cryptography to assist the biggest content owners, but advertised as something necessary and helpful for everybody. Who in fact gets any advantage out of watermarking? The private user most of the time will not really need it except for small entities of pictures maybe.
But the big enterprises do. There is a tendency to watermark more and more information in the Internet, which until now was considered as free and as a cheap method to receive information. Watermarking could stop this democratic development.
for further information see:
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4th millennium B.C.
In Sumer
Writing and calculating came into being at about the same time. The first pictographs carved into clay tablets were used for administrative purposes. As an instrument for the administrative bodies of early empires, which began to rely on the collection, storage, processing and transmission of data, the skill of writing was restricted to only very few. Being more or less separated tasks, writing and calculating converge in today's computers.
Letters are invented so that we might be able to converse even with the absent, says Saint Augustine. The invention of writing made it possible to transmit and store information. No longer the ear predominates; face-to-face communication becomes more and more obsolete for administration and bureaucracy. Standardization and centralization become the constituents of high culture and vast empires as Sumer and China.
3200 B.C.
In Sumer the seal is invented.
About 3000 B.C.
In Egypt papyrus scrolls and
About 1350 B.C.
In Assyria the cuneiform script is invented.
1200 B.C.
According to Aeschylus, the conquest of the town of Troy was transmitted via torch signals.
About 1100 B.C.
Egyptians use homing pigeons to deliver military information.
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Gopher is a menu system with hierarchically structured list of files that predates the World Wide Web.
Today Gopher is of diminishing importance and mostly replaced by the
an algorithm for bringing a legible message into an illegible form. There has to exist some sort of code book to encode/decode it.