From: couchot <couchot@couchot-laptop.(none)>
Date: Tue, 29 May 2012 20:33:39 +0000 (+0200)
Subject: analyse
X-Git-Url: https://bilbo.iut-bm.univ-fcomte.fr/and/gitweb/canny.git/commitdiff_plain/8c5cd531e59e8cba828f39f976cbe328d82ce0b2?ds=inline;hp=--cc

analyse
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+
+This work considers digital images as covers and fondation is
+spatial least significant-bit (LSB) replacement.
+I this data hiding scheme a subset of all the LSB of the cover image is modified 
+with a secret bit stream depending on to a key, the cover, and the message to embed.
+This well studied steganographic approach  never decreases (resp. increases)
+pixel with even value (resp. odd value) and may break structural symetry.
+These structural modification can be detected  by statistical approaches 
+and thus by steganalysis methods~\cite{DBLP:journals/tsp/DumitrescuWW03,DBLP:conf/mmsec/FridrichGD01,Dumitrescu:2005:LSB:1073170.1073176}
+
+This drawback is avoided in LSB matching (LSBM) where
+the $+1$ or $-1$ is randomly added to the cover pixel LSB value 
+only if this one does not match the secret bit.
+Since probabilities of increasing or decreasing pixel value are the same, statistical approaches 
+cannot be applied there to discover stego-images in LSBM.
+The most accurate detectors for this matching are universal steganalysers such as~\cite{LHS08,DBLP:conf/ih/2005,FK12}
+which classify images thanks to extracted features from neighboring elements of noise residual.  
+
+LSB matching revisited (LSBMR)~\cite{Mielikainen06} have been recently introduced. 
+For a given pair of pixels, in which the LSB
+of the first pixel carries one bit of secret message, and the relationship
+(odd–even combination) of the two pixel values carries
+another bit of secret message. 
+
+
+
+In such a way, the modification
+rate of pixels can decrease from 0.5 to 0.375 bits/pixel
+(bpp) in the case of a maximum embedding rate, meaning fewer
+changes to the cover image at the same payload compared to
+LSB replacement and LSBM. It is also shown that such a new
+scheme can avoid the LSB replacement style asymmetry, and
+thus it should make the detection slightly more difficult than the
+LSBM approach based on our experiments
+
+random LSB selection: coarse, easily tractable, easilly detactable
+
+
+
+feature-based : precise but time consuming 
+
+security need : message has to be encrypted before beeing introduced. Using efficient and secured cryptographic approach
+
+LSBR: to coarse (apply hugo breaker on it)