wok annotate outguess/description.txt @ rev 25037

Up glza (0.11.4)
author Pascal Bellard <pascal.bellard@slitaz.org>
date Sat May 21 21:38:29 2022 +0000 (2022-05-21)
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Hans-G?nter@24171 1 Outguess is a universal steganographic tool that allows
Hans-G?nter@24171 2 the insertion of hidden information into the redundant
Hans-G?nter@24171 3 bits of data sources.
Hans-G?nter@24171 4 The nature of the data source is irrelevant to the core
Hans-G?nter@24171 5 of outguess. The program relies on data specific handlers
Hans-G?nter@24171 6 that will extract redundant bits and write them back
Hans-G?nter@24171 7 after modification.
Hans-G?nter@24171 8 Currently only the PPM (Portable Pixel Map), PNM
Hans-G?nter@24171 9 (Portable Any Map), and JPEG image formats are supported,
Hans-G?nter@24171 10 although outguess could use any kind of data, as long as
Hans-G?nter@24171 11 a handler were provided.
Hans-G?nter@24171 12
Hans-G?nter@24171 13 Steganography is the art and science of hiding that
Hans-G?nter@24171 14 communication is happening.
Hans-G?nter@24171 15 Classical steganography systems depend on keeping the
Hans-G?nter@24171 16 encoding system secret, but modern steganography are
Hans-G?nter@24171 17 detectable only if secret information is known, e.g. a
Hans-G?nter@24171 18 secret key.
Hans-G?nter@24171 19 Because of their invasive nature steganography systems
Hans-G?nter@24171 20 leave detectable traces within a medium's characteristics.
Hans-G?nter@24171 21 This allows an eavesdropper to detect media that has been
Hans-G?nter@24171 22 modified, revealing that secret communication is taking
Hans-G?nter@24171 23 place. Although the secrecy of the information is not
Hans-G?nter@24171 24 degraded, its hidden nature is revealed, defeating the
Hans-G?nter@24171 25 main purpose of Steganography.
Hans-G?nter@24171 26
Hans-G?nter@24171 27 For JPEG images, OutGuess preserves statistics based on
Hans-G?nter@24171 28 frequency counts.
Hans-G?nter@24171 29 As a result, no known statistical test is able to detect
Hans-G?nter@24171 30 the presence of steganographic content.
Hans-G?nter@24171 31 Before embedding data into an image, the OutGuess system
Hans-G?nter@24171 32 can determine the maximum message size that can be hidden
Hans-G?nter@24171 33 while still being able to maintain statistics based on
Hans-G?nter@24171 34 frequency counts.
Hans-G?nter@24171 35
Hans-G?nter@24171 36 OutGuess uses a generic iterator object to select which
Hans-G?nter@24171 37 bits in the data should be modified.
Hans-G?nter@24171 38 A seed can be used to modify the behavior of the iterator.
Hans-G?nter@24171 39 It is embedded in the data along with the rest of the
Hans-G?nter@24171 40 message. By altering the seed, OutGuess tries to find a
Hans-G?nter@24171 41 sequence of bits that minimizes the number of changes in
Hans-G?nter@24171 42 the data that have to be made.