From: couchot 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=sidebyside analyse --- diff --git a/analysis.tex b/analysis.tex new file mode 100644 index 0000000..4ae4244 --- /dev/null +++ b/analysis.tex @@ -0,0 +1,44 @@ + +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)