X-Git-Url: https://bilbo.iut-bm.univ-fcomte.fr/and/gitweb/canny.git/blobdiff_plain/01ec38902455e4ee4dba09ead751639638481fd2..ff62ab9a78e83759f5e40e3b7d422fddeb45115d:/ourapproach.tex diff --git a/ourapproach.tex b/ourapproach.tex index 3537640..534fb29 100644 --- a/ourapproach.tex +++ b/ourapproach.tex @@ -48,6 +48,8 @@ Let us first focus on the data embedding. \subsection{Security considerations}\label{sub:bbs} +\JFC{To provide a self-contained article without any bias, we shortly +pressent the retained encryption process.} Among the methods of message encryption/decryption (see~\cite{DBLP:journals/ejisec/FontaineG07} for a survey) we implement the asymmetric @@ -140,7 +142,7 @@ In the former the embedding rate depends on the number of edge pixels. The higher it is, the larger the message length that can be inserted is. Practically, a set of edge pixels is computed according to the Canny algorithm with parameters $b=7$ and $T=3$. -The message length is thus defined to be less than +The message length is thus defined to be lesser than half of this set cardinality. If $x$ is too short for $m$, the message is split into sufficient parts and a new cover image should be used for the remaining part of the message. @@ -151,13 +153,13 @@ This is the classical approach adopted in steganography. Practically, the Canny algorithm generates a set of edge pixels related to increasing values of $T$ and until its cardinality -is sufficient. Even in this situation, our scheme is adapting +is sufficient. Even in this situation, our scheme adapts its algorithm to meet all the user's requirements. Once the map of possibly modified pixels is computed, two methods may further be applied to extract bits that -are really modified. +are really changed. The first one randomly chooses the subset of pixels to modify by applying the BBS PRNG again. This method is further denoted as a \emph{sample}. Once this set is selected, a classical LSB replacement is applied to embed the @@ -197,7 +199,7 @@ It is further referred to as \emph{STC} and is detailed in the next section. % the fuzzy logic edge detector. For a given set of parameters, -the canny algorithm returns a numerical value and +the Canny algorithm returns a numerical value and states whether a given pixel is an edge or not. In this article, in the Adaptive strategy we consider that all the edge pixels that @@ -226,7 +228,7 @@ follows the data embedding approach since there exists a reverse function for all its steps. More precisely, let $b$ be the most significant bits and -$T$ be the size of the canny mask, both be given as a key. +$T$ be the size of the Canny mask, both be given as a key. Thus, the same edge detection is applied on a stego content $Y$ to produce the sequence $y$ of LSBs. If the STC approach has been selected in embedding, the STC reverse @@ -358,7 +360,7 @@ V_{ij}= \left\{ 150 & \textrm{if} & \vert X_{ij} - Y_{ij} \vert = 2 \\ 225 & \textrm{if} & \vert X_{ij} - Y_{ij} \vert = 3 \end{array} -\right.. +\right. $$ This function allows to emphasize differences between contents. Notice that since $b$ is 7 in Fig.~\ref{fig:diff7}, the embedding is binary