Steganography%20with%20Digital%20Images

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Steganography with Digital Images

• By
• Karl Schramm

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Generic Stegosystem
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Embedding Guidelines

• Alteration must be invisible
• Dont alter the header
• The message must be contained in the cover data
• Use error-correcting code if possible
• Dont reuse the cover data

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LSB Modification

• Hide data by altering the LSB of a pixel
• Choose pixels pseudo-randomly
• Works with both true color and color index modes

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JPEG Algorithms

• Modify discrete cosine transform (DCT)
  coefficients
• Choose either larger coefficient values or
  coefficients in a particular range

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Patchwork

• Choose random pixel pairs
• Let d p1 p2
• Encode information with values
• d lt 0 0
• d gt 0 1
• Swap the pixels if necessary
• If d 0, choose a new pair

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Steganalysis

• Traffic analysis
• Detection
• Brute force
• Manipulation