Relecture de l'intro

[canny.git] / ourapproach.tex

diff --git a/ourapproach.tex b/ourapproach.tex
index 0f2d7b598d7b08088b6035568d6fe3b027285d6b..fc22e8f2ab2a32ee9a01b30d774b1a0a55f5a9e8 100644 (file)
--- a/ourapproach.tex
+++ b/ourapproach.tex
@@ -67,6 +67,8 @@ 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.
 
 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.
 

+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. 
 
 % First of all, let us discuss about compexity of edge detetction methods.
 % Let then $M$ and $N$ be the dimension of the original image. 


@@ -83,7 +85,7 @@ GPU. And of course, we do not pretend that this is the best solution.
 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 
+one is practically enlarged until its size is at least twice as many larger 

 than the size of embedded message.
 
 % Edge Based Image Steganography schemes 
 than the size of embedded message.
 
 % Edge Based Image Steganography schemes 


@@ -126,21 +128,24 @@ it would thus be not possible to retrieve the original one in a
 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 +157,7 @@ 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