-the better the approach is said to be.
-Contrarily, we argue that some images should not be taken as a cover because of the nature of their signal.
-Consider for instance a uniformly black image: a very tiny modification of its pixels can be easily detectable.
-The approach we propose is thus to provide a self adaptive algorithm with a high payload, which depends on the
-cover signal.
-
-For some applications it might be interesting to have a reversible procedure to compute the same edge detection pixel set for the cover and the stego image. For this, we propose to apply the edge detection algorithm not on all the bits of the image, but to exclude the LSBs.
-
-
-\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 research work, we thus propose to combine tried and
-tested techniques of signal theory (the adaptive edge detection), coding (the binary embedding), and cryptography
-(encryption of the hidden message) to compute an efficient steganographic
-scheme, which takes into consideration the cover image
-and that can be executed on small devices.
+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 detected.
+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 15,728 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, well-studied and experimented
+techniques of signal processing (adaptive edges detection),
+coding theory (syndrome-trellis codes), and cryptography
+(Blum-Goldwas\-ser encryption protocol) are combined in this research work.
+The objective is to compute an efficient steganographic
+sche\-me, whose principal characteristic is to take into
+consideration the cover image and to be compatible with small computation resources.
