ajout canny_p3-p7

[canny.git] / intro.tex

diff --git a/intro.tex b/intro.tex
index 167b7dd87dd5777b13298d9497d2c7ee4fd96ce9..4c995485716a5bc6b9d0b6babe006ab7178f5350 100644 (file)
--- a/intro.tex
+++ b/intro.tex
@@ -45,18 +45,30 @@ LSBM approach. % based on our experiments
 
 Additionally to (efficiently) modifying LSBs, there is also a need to select pixels whose value 
 modification minimizes a distortion function.
 
 Additionally to (efficiently) modifying LSBs, there is also a need to select pixels whose value 
 modification minimizes a distortion function.

-This distortion may be computed thanks to feature vectors that are embedded for instance in the steganalysers
+This distortion may be computed thanks to feature vectors that
+ are embedded for instance in the steganalysers

 referenced above. 
 referenced above. 

-The Highly Undetectable steGO (HUGO) method~\cite{DBLP:conf/ih/PevnyFB10} is one of the most efficient instance of such a scheme.
-It takes into account so-called SPAM features 
-%(whose size is larger than $10^7$) 
-to avoid over-fitting a particular 
-steganalyser. Thus a distortion measure for each pixel is individually determined as the sum of the differences between
+The Highly Undetectable steGO (HUGO) method~\cite{DBLP:conf/ih/PevnyFB10},
+WOW~\cite{conf/wifs/HolubF12}, and UNIWARD~\cite{HFD14}
+are some of the  most efficient instances of such a scheme.
+
+HUGO takes into account so-called SPAM features.
+Thus a distortion measure for each
+pixel is individually determined as the sum of the differences between

 the features of the SPAM computed from the cover and from the stego images.
 the features of the SPAM computed from the cover and from the stego images.

-Due to this features set, HUGO allows to embed messages that are $7$ times longer than the former ones with the same level of 
+The features embedded in WOW and UNIWARD are based on Wavelet-based 
+directional filter. Thus, similarelly, the distortion function is 
+the sum  of the differences between these wavelet coefficients  
+computed from the cover and from the stego images.
+
+
+Due to this distortion measures, HUGO, WOW and UNIWARD allow
+to embed messages that are $7$ times longer than the former
+ones with the same level of 

 indetectability as LSB matching. 
 indetectability as LSB matching. 

-However, this improvement is time consuming, mainly due to the distortion function
-computation. 
+However, this improvement has a larger computation cost, mainly due to
+ the distortion function
+calculus. 

 
 
 There remains a large place between random selection of LSB and feature based modification of pixel values.
 
 
 There remains a large place between random selection of LSB and feature based modification of pixel values.


@@ -126,7 +138,7 @@ The remainder of this document is organized as follows.
 Section~\ref{sec:ourapproach} presents the details of the proposed steganographic scheme and applies it on a running example. Among its technical description, 
 its adaptive aspect is emphasized.
 Section~\ref{sub:complexity} presents the overall complexity of our approach
 Section~\ref{sec:ourapproach} presents the details of the proposed steganographic scheme and applies it on a running example. Among its technical description, 
 its adaptive aspect is emphasized.
 Section~\ref{sub:complexity} presents the overall complexity of our approach

-and compares it to the HUGO's one.
+and compares it to HUGO, WOW, and UNIWARD.

 Section~\ref{sec:experiments} shows experiments on image quality, steganalysis evaluation, and compares them to the state of the art steganographic schemes.
 Finally, concluding notes and future work are given in Section~\ref{sec:concl}.
 
 Section~\ref{sec:experiments} shows experiments on image quality, steganalysis evaluation, and compares them to the state of the art steganographic schemes.
 Finally, concluding notes and future work are given in Section~\ref{sec:concl}.