X-Git-Url: https://bilbo.iut-bm.univ-fcomte.fr/and/gitweb/canny.git/blobdiff_plain/b335b39d3ad21e598f9a7172a3e95ffe0d48a736..36f33066d192d54e79b234d89f223b3f4016ff12:/ourapproach.tex?ds=sidebyside

diff --git a/ourapproach.tex b/ourapproach.tex
index 4dce984..f832695 100644
--- a/ourapproach.tex
+++ b/ourapproach.tex
@@ -41,11 +41,33 @@ scheme.
 
 \subsubsection{Edge Based Image Steganography}
 
+
 Edge Based Image Steganography schemes 
 already studied~\cite{Luo:2010:EAI:1824719.1824720,DBLP:journals/eswa/ChenCL10,DBLP:conf/ih/PevnyFB10} differ 
 how they select edge pixels, and  
 how they modify these ones.
 
+Image Quality: Edge Image Steganography
+\JFC{Raphael, les fuzzy edge detection sont souvent utilisÃ©s. 
+  il faudrait comparer les approches en terme de nombre de bits retournÃ©s,
+  en terme de complexitÃ©. } \cite{KF11}
+\RC{Ben, Ã  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 dÃ©tectable...  Finalement on devrait surement vendre notre truc en : on a choisi cet algo car il est performant en vitesse/qualitÃ©. Mais on peut aussi en utilisÃ© 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
+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
+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.
+
+
 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},
@@ -63,6 +85,27 @@ modifies canny 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.
 
+Edge Based Image Steganography schemes 
+already studied~\cite{Luo:2010:EAI:1824719.1824720,DBLP:journals/eswa/ChenCL10,DBLP:conf/ih/PevnyFB10} differ 
+how they select edge pixels, and  
+how they modify these ones.
+
+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},
+even if the fuzzy logic based edge detection methods~\cite{Tyan1993} 
+have promising results, its complexity is in $C_3 \times O(M \times N)$
+whereas the complexity on the Canny method~\cite{Canny:1986:CAE:11274.11275} 
+is in $C_1 \times O(M \times N)$ where  $C_1 < C_3$.
+\JFC{Verifier ceci...}
+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 canny 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.
 
 
 \subsubsection{Security Considerations}
@@ -82,6 +125,21 @@ it would thus be not possible to retrieve the original one in a
 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.   
 
 
 
