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Steganography |
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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:
 http://home.att.net/~tleary/
http://www.thur.de/ulf/stegano/
http://www2.prestel.co.uk/littleton/gm2_rw.htm
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:
http://www.isse.gmu.edu/~njohnson/Steganography
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