ajout canny_p3_stc.py

[canny.git] / ourapproach.tex

diff --git a/ourapproach.tex b/ourapproach.tex
index 249e1bed6954d1ce2310b52a3fec6f56efb2823c..12b3a32e57196247fac6bfca83e750c98f9d444c 100644 (file)
--- a/ourapproach.tex
+++ b/ourapproach.tex
@@ -50,11 +50,13 @@ Let us first focus on the data embedding.
 \subsection{Security considerations}\label{sub:bbs}
 Among the methods of  message encryption/decryption 
 (see~\cite{DBLP:journals/ejisec/FontaineG07} for a survey)
-we implement the Blum-Goldwasser cryptosystem~\cite{Blum:1985:EPP:19478.19501}
+we implement the asymmetric 
+Blum-Goldwasser cryptosystem~\cite{Blum:1985:EPP:19478.19501}
 that is based on the Blum Blum Shub~\cite{DBLP:conf/crypto/ShubBB82} 
 pseudorandom number generator (PRNG) and the 
 XOR binary function.
-It has been proven~\cite{DBLP:conf/crypto/ShubBB82} that this PRNG 
+The main justification of this choice 
+is that it has been proven~\cite{DBLP:conf/crypto/ShubBB82} that this PRNG 
 has the property of cryptographical security, \textit{i.e.}, 
 for any sequence of $L$ output bits $x_i$, $x_{i+1}$, \ldots, $x_{i+L-1}$,
 there is no algorithm, whose time complexity is polynomial  in $L$, and 
@@ -115,13 +117,15 @@ Moreover, to provide edge gradient value,
 the Canny algorithm computes derivatives  
 in the two directions with respect to a mask of size $T$. 
 The higher $T$ is, the coarse the approach is. Practically, 
-$T$ is set with $3$, $3$, or $7$.
+$T$ is set with $3$, $5$, or $7$.
 In our flowcharts, this step is represented by ``Edge Detection(b, T, X)''.
 
 
 Let $x$ be the sequence of these bits. 
 The next  section presents how to adapt our scheme 
-when the size of $x$  is not sufficient for the message $m$ to embed.
+with respect to the size
+of the message $m$ to embed and the size of the cover $x$.
+
 
 
  
@@ -131,7 +135,7 @@ when the size of $x$  is not sufficient for the message $m$ to embed.
 
 \subsection{Adaptive embedding rate}\label{sub:adaptive}
 Two strategies have been developed in our approach, 
-depending on the embedding rate that is either \emph{adaptive} or \emph{fixed}.
+depending on the embedding rate that is either \emph{Adaptive} or \emph{Fixed}.
 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 
@@ -170,7 +174,7 @@ It  is further referred to as \emph{STC} and is detailed in the next section.
 
 
 
-\subsection{Minimizing distortion with syndrome-trellis codes}\label{sub:stc}
+\subsection{Minimizing distortion with Syndrome-Trellis Codes}\label{sub:stc}
 \input{stc}
 
 
@@ -302,7 +306,7 @@ So, we choose to modify the same amount of bits (9,320) and keep STC optimizing
 which bits to change among  the 36,910 ones.
 
 In the two cases, about the third part of the poem is hidden into the cover. 
-Results with \emph{adaptive} and \textit{STC} strategies are presented in 
+Results with {Adaptive} and {STC} strategies are presented in 
 Fig.~\ref{fig:lenastego}.
 
 \begin{figure}[t]
@@ -345,7 +349,11 @@ V_{ij}= \left\{
 \right..
 $$
 This function allows to emphasize differences between contents.
-Notice that 
+Notice that since $b$ is 7 in Fig.~\ref{fig:diff7}, the embedding is binary 
+and this image only contains 0 and 75 values.
+Similarly, if $b$ is 6 as in Fig.~\ref{fig:diff6}, the embedding is ternary 
+and the image contains all the values in $\{0,75,150,225\}$.
+
 
 
 \begin{figure}[t]
@@ -374,8 +382,4 @@ Notice that
 \end{figure}
 
 
-Notice that since $b$ is 7 in Fig.~\ref{fig:diff7}, the embedding is binary 
-and this image only contains 0 and 75 values.
-Similarly, when $b$ is 6 as in Fig.~\ref{fig:diff6}, the embedding is ternary 
-and the image contains all the values in $\{0,75,150,225\}$.