vibha-stego - STEGANOGRAPHY by Vibha Chhatwal 01/18/12...

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Department of Computer and Information Sciences 1 01/18/12 STEGANOGRAPHY by Vibha Chhatwal
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Department of Computer and Information Sciences 2 01/18/12 Steganography is the art of hiding information in ways that prevent the detection of hidden messages - Neil F.Johnson Cryptography is “secret writing” and steganography is “cover writing” Cryptography makes the plaintext unintelligible and so the existence of some secret plaintext is evident Steganography is hiding the message in innocent-looking “containers” or “covers” such as another text file, digital images, audio and video files. Encrypting information using cryptography and concealing information using steganography is the best combination Requirements of Hiding Information Digitally The integrity of the hidden information after it has been embedded must be correct The stego object must remain unchanged to the naked eye.
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Department of Computer and Information Sciences 3 01/18/12 History Herodotus tells how Histiaeus shaved the head of his most trusted slave and tattooed it with a message which disappeared after the hair had regrown. The purpose of this message was to instigate a revolt against the Persians. During the American Revolution, invisible ink which would glow over a flame was used by both the British and Americans to communicate secretly Steganography was also used in both World Wars. German spies hid text by using invisible ink to print small dots above or below letters and by changing the heights of letter-strokes in cover texts In World War I, prisoners of war would hide Morse code messages in letters home by using the dots and dashes on i, j, t and f. During World War II, the Germans would hide data as microdots. A message sent by a German spy during World War II read: “A p parently n e utral’s p r otest i s t h oroughly d i scounted a n d i g nored. I s man h a rd h i t. B l ockade i s sue a f fects f o r p r etext embargo o n b y -products, e j ecting s u ets a n d v e getable o i ls.” By taking the second letter of every word the hidden message “Pershing sails for NY June 1” can be retrieved
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Department of Computer and Information Sciences 4 01/18/12 Application of Steganography To hide a message intended for later retrieval Copyright marking-digital watermarking and fingerprinting Steganography (covered writing, covert channels) Protection Against detection Protection Against removal Watermarking (all objects are marked in the same way) Fingerprinting (identify all objects, every object is marked specific)
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Department of Computer and Information Sciences 5 01/18/12 Types of Steganography carriers Image files as carriers using 24-bit images: too large to pass over the network using 8-bit images: prone to modification/ lossy compression Audio files as carriers Exploits imperfection of human auditory system called audio masking. In this case, weak signal is generally inaudible in loud signal.
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This note was uploaded on 01/17/2012 for the course CIS 6930 taught by Professor Staff during the Fall '08 term at University of Florida.

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vibha-stego - STEGANOGRAPHY by Vibha Chhatwal 01/18/12...

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