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Hans-G?nter@24171
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1 Outguess is a universal steganographic tool that allows
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Hans-G?nter@24171
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2 the insertion of hidden information into the redundant
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Hans-G?nter@24171
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3 bits of data sources.
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Hans-G?nter@24171
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4 The nature of the data source is irrelevant to the core
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Hans-G?nter@24171
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5 of outguess. The program relies on data specific handlers
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Hans-G?nter@24171
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6 that will extract redundant bits and write them back
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Hans-G?nter@24171
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7 after modification.
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Hans-G?nter@24171
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8 Currently only the PPM (Portable Pixel Map), PNM
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Hans-G?nter@24171
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9 (Portable Any Map), and JPEG image formats are supported,
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Hans-G?nter@24171
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10 although outguess could use any kind of data, as long as
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Hans-G?nter@24171
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11 a handler were provided.
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Hans-G?nter@24171
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12
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Hans-G?nter@24171
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13 Steganography is the art and science of hiding that
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14 communication is happening.
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Hans-G?nter@24171
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15 Classical steganography systems depend on keeping the
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Hans-G?nter@24171
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16 encoding system secret, but modern steganography are
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Hans-G?nter@24171
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17 detectable only if secret information is known, e.g. a
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Hans-G?nter@24171
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18 secret key.
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Hans-G?nter@24171
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19 Because of their invasive nature steganography systems
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Hans-G?nter@24171
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20 leave detectable traces within a medium's characteristics.
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21 This allows an eavesdropper to detect media that has been
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22 modified, revealing that secret communication is taking
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23 place. Although the secrecy of the information is not
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Hans-G?nter@24171
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24 degraded, its hidden nature is revealed, defeating the
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Hans-G?nter@24171
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25 main purpose of Steganography.
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26
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Hans-G?nter@24171
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27 For JPEG images, OutGuess preserves statistics based on
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Hans-G?nter@24171
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28 frequency counts.
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Hans-G?nter@24171
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29 As a result, no known statistical test is able to detect
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Hans-G?nter@24171
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30 the presence of steganographic content.
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Hans-G?nter@24171
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31 Before embedding data into an image, the OutGuess system
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32 can determine the maximum message size that can be hidden
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Hans-G?nter@24171
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33 while still being able to maintain statistics based on
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Hans-G?nter@24171
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34 frequency counts.
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35
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Hans-G?nter@24171
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36 OutGuess uses a generic iterator object to select which
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Hans-G?nter@24171
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37 bits in the data should be modified.
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Hans-G?nter@24171
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38 A seed can be used to modify the behavior of the iterator.
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Hans-G?nter@24171
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39 It is embedded in the data along with the rest of the
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Hans-G?nter@24171
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40 message. By altering the seed, OutGuess tries to find a
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Hans-G?nter@24171
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41 sequence of bits that minimizes the number of changes in
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Hans-G?nter@24171
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42 the data that have to be made.
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