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[canny.git] / ourapproach.tex

diff --git a/ourapproach.tex b/ourapproach.tex
index 0f2d7b598d7b08088b6035568d6fe3b027285d6b..25defad4262510b00d4bd96417172e37e9dcb3ec 100644 (file)
--- a/ourapproach.tex
+++ b/ourapproach.tex
@@ -1,8 +1,8 @@
-The flowcharts given in Fig.~\ref{fig:sch} summarize our steganography scheme denoted as to
-STABYLO for STeganography with Canny, Bbs, binarY embedding at LOw cost.
-What follows successively details all the inner steps and flow inside 
-the embedding stage (Fig.\ref{fig:sch:emb}) 
-and inside the extraction one (Fig.~\ref{fig:sch:ext}).
+The flowcharts given in Fig.~\ref{fig:sch} summarize our steganography scheme denoted by
+STABYLO, which stands for STeganography with Canny, Bbs, binarY embedding at LOw cost.
+What follows successively details all the inner steps and flows inside 
+both the embedding stage (Fig.~\ref{fig:sch:emb}) 
+and the extraction one (Fig.~\ref{fig:sch:ext}).

 
 
 \begin{figure*}[t]
 
 
 \begin{figure*}[t]


@@ -42,10 +42,10 @@ scheme.
 \subsubsection{Edge Based Image Steganography}
 
 
 \subsubsection{Edge Based Image Steganography}
 
 

-Edge Based Image Steganography schemes 
-already studied~\cite{Luo:2010:EAI:1824719.1824720,DBLP:journals/eswa/ChenCL10} differ 
-how they select edge pixels, and  
-how they modify these ones.
+The edge based image steganography schemes 
+already presented (\cite{Luo:2010:EAI:1824719.1824720,DBLP:journals/eswa/ChenCL10}) differ 
+in how carefully they select edge pixels, and  
+how they modify them.

 
 Image Quality: Edge Image Steganography
 \JFC{Raphael, les fuzzy edge detection sont souvent utilisés. 
 
 Image Quality: Edge Image Steganography
 \JFC{Raphael, les fuzzy edge detection sont souvent utilisés. 


@@ -53,21 +53,23 @@ Image Quality: Edge Image Steganography
   en terme de complexité. } \cite{KF11}
 \RC{Ben, à voir car on peut choisir le nombre de pixel avec Canny. Supposons que les fuzzy edge soient retourne un peu plus de points, on sera probablement plus détectable...  Finalement on devrait surement vendre notre truc en : on a choisi cet algo car il est performant en vitesse/qualité. Mais on peut aussi en utilisé d'autres :-)}
 
   en terme de complexité. } \cite{KF11}
 \RC{Ben, à voir car on peut choisir le nombre de pixel avec Canny. Supposons que les fuzzy edge soient retourne un peu plus de points, on sera probablement plus détectable...  Finalement on devrait surement vendre notre truc en : on a choisi cet algo car il est performant en vitesse/qualité. Mais on peut aussi en utilisé d'autres :-)}
 

-There are  many techniques to  detect edges in  images. Main methods  are filter
-edge detection methods such as Sobel  or Canny filter, low order methods such as
-first order  and second order  methods, these methods  are based on  gradient or
+Many techniques have been proposed in the literature to  detect 
+edges in  images. 
+The most common ones are filter
+edge detection methods such as Sobel  or Canny filters, low order methods such as
+first order  and second order ones. These methods  are based on  gradient or

 Laplace  operators and  fuzzy edge  methods, which  are based  on fuzzy  logic to
 highlight edges.
 
 Laplace  operators and  fuzzy edge  methods, which  are based  on fuzzy  logic to
 highlight edges.
 

-Of course, all the algorithms have  advantages and drawbacks which depend on the
-motivation  to  highlight  edges.   Unfortunately  unless testing  most  of  the
+Of course, all the algorithms have  advantages and drawbacks that depend on the
+motivations behind that edges detection.   Unfortunately  unless testing  most  of  the

 algorithms, which  would require many  times, it is  quite difficult to  have an
 accurate idea on what would produce  such algorithm compared to another. That is
 algorithms, which  would require many  times, it is  quite difficult to  have an
 accurate idea on what would produce  such algorithm compared to another. That is

-why we have  chosen Canny algorithm which is well  known, fast and implementable
-on many  kinds of architecture, such  as FPGA, smartphone,  desktop machines and
-GPU. And of course, we do not pretend that this is the best solution.
-
+why we have  chosen Canny algorithm, which is well  known, fast, and implementable
+on many  kinds of architectures like FPGAs, smartphones,  desktop machines, and
+GPUs. And of course, we do not pretend that this is the best solution.

 
 

+In order to be able to compute the same set of edge pixels, we suggest to consider all the bits of the image (cover or stego) without the LSB. With an 8 bits image, only the 7 first bits are considered. In our flowcharts, this is represented by ``LSB(7 bits Edge Detection)''.

 % First of all, let us discuss about compexity of edge detetction methods.
 % Let then $M$ and $N$ be the dimension of the original image. 
 % According to~\cite{Hu:2007:HPE:1282866.1282944},
 % First of all, let us discuss about compexity of edge detetction methods.
 % Let then $M$ and $N$ be the dimension of the original image. 
 % According to~\cite{Hu:2007:HPE:1282866.1282944},


@@ -79,12 +81,11 @@ GPU. And of course, we do not pretend that this is the best solution.
 % In experiments detailled in this article, the Canny method has been retained 
 % but the whole approach can be updated to consider 
 % the fuzzy logic edge detector.   
 % In experiments detailled in this article, the Canny method has been retained 
 % but the whole approach can be updated to consider 
 % the fuzzy logic edge detector.   

-

 Next, following~\cite{Luo:2010:EAI:1824719.1824720}, our scheme automatically
 modifies the Canny algorithm 
 parameters to get a sufficiently large set of edge bits: this 
 Next, following~\cite{Luo:2010:EAI:1824719.1824720}, our scheme automatically
 modifies the Canny algorithm 
 parameters to get a sufficiently large set of edge bits: this 

-one is practically enlarged untill its size is at least twice as many larger 
-than the size of embedded message.
+one is practically enlarged until its size is at least twice as large 
+as the size of the embedded message.

 
 % Edge Based Image Steganography schemes 
 % already studied~\cite{Luo:2010:EAI:1824719.1824720,DBLP:journals/eswa/ChenCL10,DBLP:conf/ih/PevnyFB10} differ 
 
 % Edge Based Image Steganography schemes 
 % already studied~\cite{Luo:2010:EAI:1824719.1824720,DBLP:journals/eswa/ChenCL10,DBLP:conf/ih/PevnyFB10} differ 


@@ -113,34 +114,39 @@ than the size of embedded message.
 Among 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}
 Among 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}

-which is based on the Blum Blum Shub~\cite{DBLP:conf/crypto/ShubBB82} Pseudo Random Number Generator (PRNG) 
+that is based on the Blum Blum Shub~\cite{DBLP:conf/crypto/ShubBB82} pseudorandom number generator (PRNG) 

 for security reasons.
 It has been indeed proven~\cite{DBLP:conf/crypto/ShubBB82} that this PRNG 
 has the cryptographically security property, \textit{i.e.}, 
 for security reasons.
 It has been indeed proven~\cite{DBLP:conf/crypto/ShubBB82} that this PRNG 
 has the cryptographically security property, \textit{i.e.}, 

-for any sequence $L$ of output bits $x_i$, $x_{i+1}$, \ldots, $x_{i+L-1}$,
+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 
 which allows to find $x_{i-1}$ and $x_{i+L}$ with a probability greater
 than $1/2$.
 there is no algorithm, whose time complexity is polynomial  in $L$, and 
 which allows to find $x_{i-1}$ and $x_{i+L}$ with a probability greater
 than $1/2$.

-Thus, even if the encrypted message would be extracted, 
-it would thus be not possible to retrieve the original one in a 
+Equivalent formulations of such a property can
+be found. They all lead to the fact that,
+even if the encrypted message is extracted, 
+it is impossible to retrieve the original one in 

 polynomial time.   
 
 
 polynomial time.   
 
 

-\subsubsection{Security Considerations}
-Among 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}
-which is based on the Blum Blum Shub~\cite{DBLP:conf/crypto/ShubBB82} Pseudo Random Number Generator (PRNG) 
-for security reasons.
-It has been indeed proven~\cite{DBLP:conf/crypto/ShubBB82} that this PRNG 
-has the cryptographically security property, \textit{i.e.}, 
-for any sequence $L$ of output bits $x_i$, $x_{i+1}$, \ldots, $x_{i+L-1}$,
-there is no algorithm, whose time complexity is polynomial  in $L$, and 
-which allows to find $x_{i-1}$ and $x_{i+L}$ with a probability greater
-than $1/2$.
-Thus, even if the encrypted message would be extracted, 
-it would thus be not possible to retrieve the original one in a 
-polynomial time.   
+%%RAPH: paragraphe en double :-)
+
+%% \subsubsection{Security Considerations}
+%% Among 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}
+%% which is based on the Blum Blum Shub~\cite{DBLP:conf/crypto/ShubBB82} Pseudo Random Number Generator (PRNG) 
+%% for security reasons.
+%% It has been indeed proven~\cite{DBLP:conf/crypto/ShubBB82} that this PRNG 
+%% has the cryptographically security property, \textit{i.e.}, 
+%% for any sequence $L$ of output bits $x_i$, $x_{i+1}$, \ldots, $x_{i+L-1}$,
+%% there is no algorithm, whose time complexity is polynomial  in $L$, and 
+%% which allows to find $x_{i-1}$ and $x_{i+L}$ with a probability greater
+%% than $1/2$.
+%% Thus, even if the encrypted message would be extracted, 
+%% it would thus be not possible to retrieve the original one in a 
+%% polynomial time. 
+

 
 
 
 
 
 


@@ -152,7 +158,7 @@ polynomial time.
 \subsection{Data Extraction}
 Message extraction summarized in Fig.~\ref{fig:sch:ext} follows data embedding
 since there exists a reverse function for all its steps.
 \subsection{Data Extraction}
 Message extraction summarized in Fig.~\ref{fig:sch:ext} follows data embedding
 since there exists a reverse function for all its steps.

-First of all, the same edge detection is applied to get set,
+First of all, the same edge detection is applied (on the 7 first bits) to get set,

 which is  sufficiently large with respect to the message size given as a key.  
 Then the STC reverse algorithm is applied to retrieve the encrypted message.
 Finally, the Blum-Goldwasser decryption function is executed and the original
 which is  sufficiently large with respect to the message size given as a key.  
 Then the STC reverse algorithm is applied to retrieve the encrypted message.
 Finally, the Blum-Goldwasser decryption function is executed and the original