X-Git-Url: https://bilbo.iut-bm.univ-fcomte.fr/and/gitweb/hdrcouchot.git/blobdiff_plain/596713f36ad5e56e5860473b80cfcd4821a616c8..1cd71ddffbb51c7d43136d4b00cf09158105ddd5:/ahmad.tex?ds=sidebyside

diff --git a/ahmad.tex b/ahmad.tex
index f1612a8..0ebbdb5 100644
--- a/ahmad.tex
+++ b/ahmad.tex
@@ -2,37 +2,19 @@ En Ã©tudiant le watermarking,
 nous avons constatÃ© que trÃ¨s peu de travaux ciblaient les documents PDF
 qui reprÃ©sentent cependant une part non anecdotique des donnÃ©es
 Ã©changÃ©es en ligne.
+Parmi ces travaux, \cite{PD2008} propose la modification du nombre 
+d'espaces entre les mots ou entre les paragraphes.
+Similairement, les auteurs  de~\cite{DBLP:journals/sigpro/LeeT10}
+ajoutent des caractÃ¨res invisibles dans le document.
+En supprimant ces espaces ou caractÃ¨res invisibles, la marque s'enlÃ¨ve
+facilement.
+Dans~\cite{PD2008}, les auteurs modifient de maniÃ¨re imperceptible
+le positionnements des caractÃ¨res. D'autres Ã©lÃ©ments de postionnement
+sont intÃ©grÃ©s dans~\cite{WT08}.
+Une attaque qui remodifierait  alÃ©atoirement de maniÃ¨re faible ces positions
+ dÃ©truirait la marque dans les deux cas.
 
 
-Several methods of  Steganography and Digital Watermarking  in PDF and
-Text documents have been proposed. In~\cite{PD2008}, a steganographic approach
-is   presented   by   hiding    information   using   inter-word   and
-inter-paragraph  spacing in  a  text. The  main  disadvantage of  this
-method is that the hidden message  can be destroyed by simply deleting
-some  spaces between  the  words  in the  stego  text.  In~\cite{PD2008},
-two
-different  algorithms   are  proposed  which  are   considered  as  an
-alternative  for the  original  TJ operator  method.  The TJ  operator
-displays  the  text  string  in  a  PDF  document,  allows  individual
-character positioning  and uses character and  word spacing parameters
-from  the  text  state.  The alternative  method  has  less  embedding
-capacity than the  original method. In~\cite{LLGC13}  an encryption technique
-is  proposed by  combining  the information  hiding  technique in  PDF
-documents and  the quadratic  residue as  basis and  then apply  it to
-copyright protection and  digital learning. The main  drawback of this
-method is  that the hidden  message can be  easly removed. In~\cite{DBLP:journals/sigpro/LeeT10}, an
-embedding method in  source programs using invisible  $ASCII$ codes is
-proposed. This method is very easy  to detect by simply extracting the
-modified  text  from  the  document,  converting  it  to  hexadecimal,
-extracting all  the inserted  invisible $ASCII$ characters,  and then,
-decoding the embedded message.  In~\cite{WT08}, a data hiding in PDF files and
-applications by  imperceivable modifications of PDF  object parameters
-is proposed. This  method serves to hide data  by slight modifications
-of the values  of various PDF object parameters such  as media box and
-text   matrices.  The   method  is   considered  to   have  sufficient
-transparency  while  its  main  drawback is  its  very  low  embedding
-capacity.
-
 Substitutive   Quantization  Index   Modulation  (QIM)   methods  were
 introduced  by Chen  and Wornell~\cite{CW01}. The  Spread Transform  Dither
 Modulation (STDM) is an implementation of  this scheme and it has been
