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--- security:steganography [2011/11/21 12:26] – [Steganalysis of the LSB method] cedric
+++ security:steganography [2021/06/27 00:36] (current) – cedric
@@ Line 1: / Line 1: @@
+====== Installation of Stegano ======
+For the examples you need to install Stegano.
+<code bash>
+sudo pip install Stegano
+</code>
+You can read the [[http://stegano.readthedocs.io | documentation of Stegano]] (included in the sources).
 ====== Steganography ======
 Steganography is the art and science of writing hidden messages.
@@ Line 10: / Line 22: @@
 We will dive into digital steganography.
-The folowing sections will present some techniques of digital steganography.
+The following sections will present some techniques of digital steganography.
 ===== Simple steganography art =====
-In computer scinece a well known method of hiding data (message) is to concatenate these data to an archive.
+In computer science a well known method of hiding data (message) is to concatenate these data to an archive.
 For example, if I want to hide a text file in a music file:
@@ Line 116: / Line 128: @@
 </code>
-This is a very simple example showing how to hide a string in an image with the LSB method. Have a look in the [[http://bitbucket.org/cedricbonhomme/stegano/src/tip/lsb-s.py | source code of Stéganô]] to find more details.
+This is a very simple example showing how to hide a string in an image with the LSB method.
 ====== Steganalysis ======
@@ Line 131: / Line 143: @@
 {{ :security:2010-08-04t15:42:06_enc_steganalysed.png?|Steganalysis of the image with hidden text}}
-This technique simply consist to replace even number of pixels components by 0 and odd components by 255. This means that the pixel (132, 247, 123) become (0, 255, 255).
+This technique simply consist to replace odd components by 255 and even number by 0. This means that the pixel (132, 247, 123) become (0, 255, 255).
+===== Steganalysis of the LSB method with sets =====
+You must [[security:steganography#installation_of_stegano|install Stegano]] before running these commands.
+First, we will hide a message in a picture with the simple LSB method and with the LSB method + sets.
+<code bash>
+$ cd stegano
+# LSB with The Eratosthenes set
+$ slsb-set --hide -i ./examples/pictures/Montenach.png -o ~/Montenach-enc-gen.png --generator eratosthenes -f ./examples/lorem_ipsum.txt
+# LSB only
+$ slsb --hide -i ./examples/pictures/Montenach.png -o ~/Montenach-enc.png  -f ../examples/lorem_ipsum.txt
+</code>
+The selected generator //Sieve of Eratosthenes// (''--generator eratosthenes'') will generate the set of points. This set of points will be used in order to select the pixels where the informations will be hidden.
+The following will generate the corresponding steganalysed pictures (left column):
+<code bash>
+# Steganalysis of the original image
+$ steganalysis-parity -i ../examples/pictures/Montenach.png -o ~/Montenach-steg.png
+# Steganalysis of the image with hidden text (LSB only)
+$ steganalysis-parity -i ~/Montenach-enc.png -o ~/Montenach-enc-steg.png
+# Steganalysis of the image with hidden text (LSB + Eratosthenes)
+$ steganalysis-parity -i ~/Montenach-enc-gen.png -o ~/Montenach-enc-gen-steg.png
+</code>
+{{:security:montenach.png?700*500|Original image}}
+{{ :security:montenach-steg.png?700*500|(1) Steganalysis of the original image}}
+{{:security:montenach-enc.png?700*500|Image with hidden text  (LSB only)}}
+{{ :security:Montenach-enc-steg.png?700*500|(2) Steganalysis of the image with hidden text (LSB only)}}
+{{:security:montenach-enc-gen.png?700*500|Image with hidden text  (LSB + Eratosthenes)}}
+{{ :security:montenach-enc-gen-steg.png?700*500|(3) Steganalysis of the image with hidden text (LSB + Eratosthenes)}}
+Compare the pictures 1 and  2 and compare the pictures 1 and 3, left column.
+==== Reveal the message ====
+<code bash>
+$ slsb-set --reveal --generator eratosthenes -i ~/Montenach-enc-gen.png -b ~/file-gen.txt
+$ slsb --reveal  -i ~/Montenach-enc.png -b ~/file.txt
+$ cmp ~/file-gen.txt ~/file.txt
+$ cat ~/file.txt
+Lorem ipsum dolor sit amet, consectetur adipiscing elit. Nam placerat fermentum
+lorem, at porttitor metus congue eu. Mauris vitae tell
+.
+.
+.
+$ slsb-set --reveal --generator fermat -i ~/Montenach-enc-gen.png -b ~/file.txt
+Impossible to detect message.
+$ slsb-set --reveal --generator mersenne -i ~/Montenach-enc-gen.png -b ~/file.txt
+Impossible to detect message.
+</code>
 ====== Bibliography ======