-Edges form the outline of an object: they are the boundary between overlapping objects or between an object
-and the background. A small modification of pixel value in the stego image should not be harmful to the image quality:
-in cover image, edge pixels already break its continuity and thus already contains large variation with neighbouring
-pixels. In other words, minor changes in regular area are more dramatic than larger modifications in edge ones.
-Our proposal is thus to embed message bits into edge shapes while preserving other smooth regions.
-
-Edge based steganographic schemes have bee already studied~\cite{Luo:2010:EAI:1824719.1824720,DBLP:journals/eswa/ChenCL10}.
-In the former, the authors show how to select sharper edge regions with respect
-to embedding rate: the larger the number of bits to be embedded, the coarse the edge regions are.
-Then the data hiding algorithm is achieved by applying LSBMR on pixels of this region.
-The authors show that this method is more efficient than all the LSB, LSBM, LSBMR approaches
-thanks to extensive experiments.
-However, it has been shown that the distinguish error with LSB embedding is fewer than the one with some binary embedding~\cite{DBLP:journals/tifs/FillerJF11}.
-We thus propose to take benefit of these optimized embedding, provided it is not too time consuming.
-Experiments have confirmed such a fact\JFC{Raphael....}.
-
-
-\JFC{Christophe : énoncer la problématique du besoin de crypto et de ``cryptographiquement sûr'', les algo déjà cassés....
-l'efficacité d'un encodage/décodage ...}
-To deal with security issues, message is encrypted
-
-In this paper, we thus propose to combine tried and tested techniques of signal theory (the adaptive edge detection), coding (the binary embedding), and cryptography
-(the encrypt the message) to compute an efficient steganography scheme that is amenable to be executed on small devices.
-
-The rest of the paper is organised as follows.
-Section~\ref{sec:ourapproach} presents the details of our steganographic scheme.
-Section~\ref{sec:experiments} shows experiments on image quality, steganalytic evaluation, complexity of our approach
-and compare them to state of the art steganographic schemes.
-Finally, concluding notes and future works are given in section~\ref{sec:concl}
-
-
+Edges form the outline of an object: they are the boundaries between overlapping objects or between an object
+and its background. When producing the stego-image, a small modification of some pixel values in such edges should not impact the image quality, which is a requirement when
+attempting to be undetectable. Indeed,
+in a cover image, edges already break the continuity of pixels' intensity map and thus already present large variations with their neighboring
+pixels. In other words, minor changes in regular areas are more dramatic than larger modifications in edge ones.
+Our first proposal is thus to embed message bits into edge shapes while preserving other smooth regions.
+
+Edge based steganographic schemes have already been studied,
+the most interesting
+approaches being detailed in~\cite{Luo:2010:EAI:1824719.1824720} and
+in~\cite{DBLP:journals/eswa/ChenCL10}.
+In the former, the authors present the Edge Adaptive
+Image Steganography based on LSB matching revisited further denoted as
+EAISLSBMR. This approach selects sharper edge
+ regions with respect
+to a given embedding rate: the larger the number of bits to be embedded is, the coarser
+the edge regions are.
+Then the data hiding algorithm is achie\-ved by applying LSBMR on some of the pixels of these regions.
+The authors show that their proposed method is more efficient than all the LSB, LSBM, and LSBMR approaches
+through extensive experiments.
+However, it has been shown that the distinguishing error with LSB embedding is lower than
+the one with some binary embedding~\cite{DBLP:journals/tifs/FillerJF11}.
+We thus propose to take advantage of this optimized embedding, provided they are not too time consuming.
+In the latter, an hybrid edge detector is presented followed by an ad hoc
+embedding.
+The Edge detection is computed by combining fuzzy logic~\cite{Tyan1993}
+and Canny~\cite{Canny:1986:CAE:11274.11275} approaches.
+The goal of this combination
+is to enlarge the set of modified bits to increase the payload of the data hiding scheme.
+
+
+One can notice that all the previously referenced
+sche\-mes~\cite{Luo:2010:EAI:1824719.1824720,DBLP:journals/eswa/ChenCL10,DBLP:conf/ih/PevnyFB10}
+produce stego contents
+by only considering the payload, not the type of image signal: the higher the payload is,
+the better the approach is said to be.
+For instance, studied payloads range from 0.04 to 0.4 modified bits per pixel.
+Contrarily, we argue that some images should not be taken
+as a cover because of the nature of their signals.
+Consider for instance a uniformly black image: a very tiny modification of its
+pixels can be easily detectable.
+Practically speaking, if Alice would send
+a hidden message to Bob, she would never consider
+such kind of image and a high embedding rate.
+The approach we propose here is thus to provide a small complexity
+self adaptive algorithm
+with an acceptable payload, which
+depends on the cover signal.
+The payload is further said to
+ be acceptable if it allows to embed a sufficiently
+long message in the cover signal.
+Practically speaking, our approach is efficient enough for
+payloads close to 0.06 bit per pixel which allows to embed
+messages of length larger than 16000 bits in an
+image of size $512\times 512$ pixels.
+
+% Message extraction is achieved by computing the same
+% edge detection pixels set for the cover and the stego image.
+% The edge detection algorithm is thus not applied on all the bits of the image,
+% but to exclude the LSBs which are modified.
+
+Finally, even if the steganalysis discipline
+ has known great innovations these last years, it is currently impossible to prove rigorously
+that a given hidden message cannot be recovered by an attacker.
+This is why we add to our scheme a reasonable
+message encryption stage, to be certain that,
+even in the worst case scenario, the attacker
+will not be able to obtain the original message content.
+Doing so makes our steganographic protocol, to a certain extend, an asymmetric one.
+
+To sum up, in this research work, well-studied and experimented
+techniques of signal processing (adaptive edges detection),
+coding theory (syndrome-trellis codes), and cryptography
+(Blum-Goldwasser encryption protocol) are combined
+to compute an efficient steganographic
+scheme, whose principal characteristic is to take into
+consideration the cover image and to be compatible with small computation resources.
+
+The remainder of this document is organized as follows.
+Section~\ref{sec:ourapproach} presents the details of the proposed steganographic scheme and applies it on a running example. Among its technical description,
+its adaptive aspect is emphasized.
+Section~\ref{sub:complexity} presents the overall complexity of our approach
+and compares it to HUGO, WOW, and UNIWARD.
+Section~\ref{sec:experiments} shows experiments on image quality, steganalysis evaluation, and compares them to the state of the art steganographic schemes.
+Finally, concluding notes and future work are given in Section~\ref{sec:concl}.
