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\language english
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\author "Anonymous" 
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\begin_body

\begin_layout Title
Watermarking Source Code
\end_layout

\begin_layout SubTitle
version 0.5
\end_layout

\begin_layout Author
Peter Meerwald
\end_layout

\begin_layout Address
Dept.
 of Computer Sciences, University of Salzburg
\newline
Jakob-Haringer-Str.
 2, A-5020 Salzburg, Austria
\newline

\begin_inset LatexCommand url
target "mailto:pmeerw@cosy.sbg.ac.at"

\end_inset


\newline

\begin_inset LatexCommand url
target "http://www.cosy.sbg.ac.at/~pmeerw/Watermarking"

\end_inset


\end_layout

\begin_layout Abstract
This package provides source code for some watermarking algorithms in hopefully
 portable C code.
 The programs can be used to study watermarking techniques, perform comparative
 robustness tests and develop new attacks against embedded watermarks.
\end_layout

\begin_layout Abstract
However, the provided programs are by no means suitable for real-world applicati
on (i.e.
 copyright protection) and the code solely serves some educational purpose.
\end_layout

\begin_layout Standard
\begin_inset LatexCommand tableofcontents

\end_inset


\end_layout

\begin_layout Section
Introduction
\end_layout

\begin_layout Standard
Academic research in the watermarking field has grown dramatically since
 approximately 1995.
 But surprisingly, source code for the proposed watermarking schemes has
 not been made available.
 The reason is most likely the security of many watermarking systems lies
 at least to some extent in the embedding and detection algorithm itself,
 and not in the keys used -- violating the Kerckhoff principle 
\begin_inset LatexCommand cite
key "Kerckhoff1883a"

\end_inset

.
\end_layout

\begin_layout Standard
With the availability of public robustness test for watermarking algorithms,
 StirMark 
\begin_inset LatexCommand cite
key "Petitcolas99c, Petitcolas98b, Petitcolas98a"

\end_inset

, Unzign
\begin_inset Foot
status collapsed

\begin_layout Standard
\begin_inset LatexCommand url
target "http://www.altern.org/watermark"

\end_inset


\end_layout

\end_inset

 and very recently Checkmark
\begin_inset LatexCommand cite
key "Pereira01b"

\end_inset

, the situation begins to improve.
 Now it is possible to measure the performance of watermarking systems.
 
\end_layout

\begin_layout Standard
In order the compare and evaluate new embedding and detection techniques,
 it is also necessary to have some reference implementations of the older,
 now often called classical schemes.
 In this work, we provide some implementations of watermarking schemes,
 some of which can be considered 'classical'.
\end_layout

\begin_layout Standard
It was the goal to capture the main ideas of the proposed algorithms, as
 layed out in the respective papers.
 This is clearly not an easy task as some papers do not disclose all details
 or state which particular parameters were used to obtain the results outlined
 in the communications.
\end_layout

\begin_layout Standard
I am very interested in hearing your comments, complaints and suggestions
 regarding this software.
 Moreover, if you have source code for a watermarking scheme not yet covered
 or some useful utility I would be happy to include your code in this distributi
on.
 Please see the contact information at the top of this document.
\end_layout

\begin_layout Standard
If you use the accompanying code, please cite my thesis:
\end_layout

\begin_layout Quotation
Peter Meerwald, Digital Image Watermarking in the Wavelet Transform Domain,
 Master's Thesis, Department of Scientific Computing, University of Salzburg,
 Austria, January 2001.
\end_layout

\begin_layout Section
Software
\end_layout

\begin_layout Standard
Most of the software provided herein was written by myself, as part of my
 Master thesis.
 Some contributions were made by Vassilis Fotopoulos
\begin_inset Foot
status collapsed

\begin_layout Standard
\begin_inset LatexCommand url
target "mailto:vfotop1@physics.upatras.gr"

\end_inset


\end_layout

\end_inset

.
 The software in the archive is organized in the following sub-directories:
\end_layout

\begin_layout Description
Fotopoulos/ contains contributions by Vassilis Fotopoulos
\end_layout

\begin_layout Description
Meerwald/ contains my work
\end_layout

\begin_layout Description
images/ contains the Lena image in PGM format; the default parameters of
 most algorithms are tuned to work best with that image
\end_layout

\begin_layout Description
linux_bin/ the place where the Linux executables are stored in the binary
 distribution
\end_layout

\begin_layout Description
win32_bin/ the place where Windows 32-bit executables are distributed; tested
 with Windows NT 4.0 only
\end_layout

\begin_layout Description
make/ contains the 
\family typewriter
\size small
Makefile
\family default
\size default
 options to build the code on supported platforms
\end_layout

\begin_layout Standard
For the purpose of this software package, a watermarking system comprises
 four parts, namely: signature generation, watermark embedding, watermark
 extraction and signature comparison or detection -- with the exception
 of Vassilis's code; there are only cast and test programs (corresponds
 to watermark embedding and detection).
 Signature is used more less as a synonym for mark and can be thought of
 as the payload (at least for some schemes :-).
\end_layout

\begin_layout Standard
All programs only accept the image in NetPBM format and will also produce
 only NetPBM-format files (see section 
\begin_inset LatexCommand ref
reference "sec:prereq"

\end_inset

).
 Unfortunately, most programs have only been tested with 8-bit gray-scale
 images of size 
\begin_inset Formula $512\times512.$
\end_inset

 
\end_layout

\begin_layout Standard
In order to simplify batch testing, the programs allow to read either from
 a file, e.g.
\end_layout

\begin_layout Standard

\family typewriter
\size small
wm_cox_e -s cox.sig
\family default
 
\family typewriter
\series bold
image.pgm
\end_layout

\begin_layout Standard
or from standard input, i.e.
\end_layout

\begin_layout Standard
wm_cox_e -s cox.sig 
\series bold
< image.pgm
\end_layout

\begin_layout Standard
The output is usually written to standard output, i.e.
 
\end_layout

\begin_layout Standard

\family typewriter
\size small
wm_cox_e -s cox.sig image.pgm
\family default
 
\family typewriter
\series bold
> wm_image.pgm
\end_layout

\begin_layout Standard
unless redirected to a file, e.g.
\end_layout

\begin_layout Standard

\family typewriter
\size small
wm_cox_e -s cox.sig
\family default
 
\family typewriter
\series bold
-o wm_image.pgm
\family default
\series default
 
\family typewriter
image.pgm
\end_layout

\begin_layout Subsection
Featured algorithms
\end_layout

\begin_layout Standard
Currently it includes the following watermarking algorithms
\end_layout

\begin_layout Itemize
Bruyndonckx [bruyn], refer to
\end_layout

\begin_layout Quotation
O.
 Bruyndonckx, Jean-Jacques Quisquater, and Benoit M.
 Macq.
 Spatial method for copyright labeling of digital images.
 In IEEE Workshop on Nonlinear Signal and Image Processing '95, Thessaloniki,
 Greece, pages 456 - 459, 1995.
\end_layout

\begin_layout Itemize
Corvi, refer to
\end_layout

\begin_layout Quotation
Marco Corvi and Gianluca Nicchiotti.
 Wavelet-based image watermarking for copyright protection.
 In Scandinavian Conference on Image Analysis SCIA '97, Lappeenranta, Finland,
 June 1997.
\end_layout

\begin_layout Itemize
Cox, refer to
\end_layout

\begin_layout Quotation
Ingemar J.
 Cox, Joe Kilian, Tom Leighton, and Talal G.
 Shamoon.
 Secure spread spectrum watermarking for multimedia.
 In Proceedings of the IEEE ICIP '97, volume 6, pages 1673 - 1687, Santa
 Barbara, California, USA, 1997.
\end_layout

\begin_layout Itemize
Dugad, refer to
\end_layout

\begin_layout Quotation
Rakesh Dugad, Krishna Ratakonda, and Narendra Ahuja.
 A new wavelet-based scheme for watermarking images.
 In Proceedings of the IEEE International Conference on Image Processing,
 ICIP '98, Chicago, IL, USA, October 1998.
 
\end_layout

\begin_layout Itemize
Fridrich (2.
 scheme), refer to
\end_layout

\begin_layout Quotation
Jiri Fridrich.
 Combining low-frequency and spread spectrum watermarking.
 In Proceedings of the SPIE Symposium on Optical Science, Engineering and
 Instrumentation, San Diego, USA, July 1998.
 
\end_layout

\begin_layout Itemize
Kim, refer to 
\end_layout

\begin_layout Quotation
Jong Ryul Kim and Young Shik Moon.
 A robust wavelet-based digital watermark using level-adaptive thresholding.
 In Proceedings of the 6th IEEE International Conference on Image Processing
 ICIP '99, page 202, Kobe, Japan, October 1999.
\end_layout

\begin_layout Itemize
Koch, refer to
\end_layout

\begin_layout Quotation
Eckhard Koch and Jian Zhao.
 Towards robust and hidden image copyright labeling.
 In Proceedings of the IEEE International Workshop on Nonlinear Signal and
 Image Processing, pages 452 - 455, Halkidiki, Marmaras, Greece, June 1995.
\end_layout

\begin_layout Itemize
Kundur, refer to 
\end_layout

\begin_layout Quotation
Deepa Kundur and Dimitrios Hatzinakos.
 Digital watermarking using multiresolution wavelet decomposition.
 In Proceedings of IEEE ICASSP '98, volume 5, pages 2969-2972, Seattle,
 WA, USA, May 1998.
 
\end_layout

\begin_deeper
\begin_layout Standard
and 
\end_layout

\end_deeper
\begin_layout Quotation
Deepa Kundur and D.
 Hatzinakos.
 Diversity and attack characterization for improved robust watermarking.
 IEEE Transactions on Signal Processing, 29(10):2383-2396, October 2001.
\end_layout

\begin_layout Itemize
Wang, refer to
\end_layout

\begin_layout Quotation
Houng-Jyh Wang, Po-Chyi Su, and C.-C.
 Jay Kuo.
 Wavelet-based digital image watermarking.
 Optics Express, volume 3, pp.
 497, December 1998.
 
\end_layout

\begin_layout Itemize
Xia, refer to
\end_layout

\begin_layout Quotation
Xiang-Gen Xia, Charles G.
 Boncelet, and Gonzalo R.
 Arce.
 Wavelet transform based watermark for digital images.
 Optics Express, volume 3, pp.
 497, December 1998.
\end_layout

\begin_layout Itemize
Xie, refer to
\end_layout

\begin_layout Quotation
Liehua Xie and Gonzalo R.
 Arce.
 Joint wavelet compression and authentication watermarking.
 In Proceedings of the IEEE International Conference on Image Processing,
 ICIP '98, Chicago, IL, USA, 1998.
\end_layout

\begin_layout Itemize
Zhu, refer to
\end_layout

\begin_layout Quotation
Wenwu Zhu, Zixiang Xiong, and Ya-Qin Zhang.
 Multiresolution watermarking for images and video: a unified approach.
 In Proceedings of the IEEE International Conference on Image Processing,
 ICIP '98, Chicago, IL, USA, October 1998.
 
\end_layout

\begin_layout Itemize
Piva/Fotopoulos [cast|test-pv,hart,sub], contribution by Vassilis Fotopoulos,
 refer to
\end_layout

\begin_layout Quotation
M.Barni, F.
 Bartolini, V.
 Cappellini, A.
 Piva.
 A DCT-Domain System for Robust Image Watermarking, Signal Processing, vol.
 66, pp 357 - 372, 1998.
\end_layout

\begin_deeper
\begin_layout Standard
\begin_inset VSpace smallskip
\end_inset

and
\begin_inset VSpace smallskip
\end_inset


\end_layout

\end_deeper
\begin_layout Quotation
V.
 Fotopoulos, A.
 N.
 Skodras, A Subband DCT approach to image watermarking, X European Signal
 Processing Conference, September 4 - 8, 2000, Tampere, Finland.
\end_layout

\begin_layout Standard
More algorithms will be added over time, I have implemented about 13 watermarkin
g algorithms in the spatial-, DCT-, and wavelet domain so far.
\end_layout

\begin_layout Subsection
\begin_inset LatexCommand label
name "sec:utility_programs"

\end_inset

Utility programs
\end_layout

\begin_layout Standard
A good way to check the effect of a watermarking algorithm is computing
 the difference image, i.e.
 subtracting the original image from the watermarked image.
 Alternatively, one can also have a look at the modified coefficients in
 the transform domain.
 The following programs facilitate these tasks:
\end_layout

\begin_layout Description
cmp_pgm compute difference image, PSNR, ...
\end_layout

\begin_layout Description
cmp_dct compute full-frame DCT domain difference image
\end_layout

\begin_layout Description
cmp_dct8x8 compute 8x8 block-based DCT difference image
\end_layout

\begin_layout Description
cmp_dwt compute DWT domain difference image
\end_layout

\begin_layout Standard
For example, to produce the difference image of two PGM files and compute
 the PSNR along with some other measures, the following command can be used:
\end_layout

\begin_layout Standard

\family typewriter
\size small
cmp_pgm -p -i original.pgm -o diff.pgm watermarked.pgm
\end_layout

\begin_layout Section
Usage
\end_layout

\begin_layout Standard
Note, almost all programs will output usage information if called with the
 
\family typewriter
\size small
-h
\family default
\size default
 argument.
\end_layout

\begin_layout Subsection
Generating a mark
\end_layout

\begin_layout Standard
First, you have to generate an appropriate signature file for the corresponding
 embedding/detection algorithm; e.g.
 if you are going to use Cox' scheme, then you would run
\end_layout

\begin_layout Standard

\family typewriter
\size small
gen_cox_sig
\end_layout

\begin_layout Standard
The programs outputs some parameters and a sequence of Gaussian distributed
 random numbers (which is the watermark sequence).
 You want to save that into a signature file, so you run
\end_layout

\begin_layout Standard

\family typewriter
\size small
gen_cox_sig > cox.sig or 
\end_layout

\begin_layout Standard

\family typewriter
\size small
gen_cox_sig -o cox.sig
\end_layout

\begin_layout Standard
You can influence e.g.
 the embedding strength that will be used in the embedding step by running
\end_layout

\begin_layout Standard

\family typewriter
\size small
gen_cox_sig -a 0.5 > too_strong_cox.sig
\end_layout

\begin_layout Standard
Usually, the programs for generating a signature will supply reasonable
 default values for marking a 8-bit gray-scale image of size 
\begin_inset Formula $512\times512.$
\end_inset


\end_layout

\begin_layout Subsection
Watermark embedding
\end_layout

\begin_layout Standard
Watermark embedding is performed with the following command (for our example,
 we are using Cox' scheme):
\end_layout

\begin_layout Standard

\family typewriter
\size small
wm_cox_e -s cox.sig -o cox_lena.pgm lena.pgm
\end_layout

\begin_layout Standard
The signature file is parsed to obtain the particular watermark sequence
 and the embedding strength.
 The watermarked image is written to the file 
\family typewriter
\size small
cox_lena.pgm
\family default
\size default
.
 Now it the time to check the perceptual quality of the produced image and
 also have a look at the difference image (see section 
\begin_inset LatexCommand ref
reference "sec:utility_programs"

\end_inset

).
\end_layout

\begin_layout Subsection
Watermark extraction
\end_layout

\begin_layout Standard
To extract the embedded signature, we execute the command 
\end_layout

\begin_layout Standard

\family typewriter
\size small
wm_cox_d -s cox.sig -i lena.pgm -o cox.wm cox_lena.pgm 
\end_layout

\begin_layout Standard
Since Cox' algorithm is not blind, the original image is needed as a reference
 to extract the embedded mark.
 The embedded mark will be stored in 
\family typewriter
\size small
cox.wm
\family default
\size default
.
 The original signature, 
\family typewriter
\size small
cox.sig
\family default
\size default
, is used to get the auxiliary embedding parameter correct (e.g.
 embedding strength).
 
\end_layout

\begin_layout Subsection
Comparing the mark
\end_layout

\begin_layout Standard
The final step is comparing the original signature against the extracted
 signature.
 The result here is usually a correlation factor.
 Values around 0 indicate that the mark has not been found, values around
 1.
\end_layout

\begin_layout Standard
In most programs a analytical detection threshold for some detection probability
 is not used.
 Hence, one has to observe the output of the detector for many different
 keys (around 1000 I'd suggest) to establish a reasonable threshold for
 detection.
 A good value to go with initially might be 0.2 which means we claim the
 watermark detected if the correlation factor is > 0.2.
\end_layout

\begin_layout Standard
The appropriate command for comparing the mark is
\end_layout

\begin_layout Standard

\family typewriter
\size small
cmp_cox_sig -s cox.sig cox.wm 
\end_layout

\begin_layout Subsection
Batch testing - benchmarking
\end_layout

\begin_layout Standard
If you want to run many test you can pipe the images to be do be watermarked
 (and tested) through the embedder and detector.
 The programs then act like a filter.
 Try something like the following in a Unix shell script:
\end_layout

\begin_layout Standard

\family typewriter
\size small
gen_cox_sig > cox.sig 
\end_layout

\begin_layout Standard

\family typewriter
\size small
for i in *.pgm 
\end_layout

\begin_layout Standard

\family typewriter
\size small
do 
\end_layout

\begin_layout Standard

\family typewriter
\size small
\InsetSpace ~
\InsetSpace ~
wm_cox_e -s cox.sig $i | 
\backslash

\end_layout

\begin_layout Standard

\family typewriter
\size small
\InsetSpace ~
\InsetSpace ~
wm_cox_d -s cox.sig -i $i | 
\backslash

\end_layout

\begin_layout Standard

\family typewriter
\size small
\InsetSpace ~
\InsetSpace ~
cmp_cox_sig -s cox.sig 
\end_layout

\begin_layout Standard

\family typewriter
\size small
done
\end_layout

\begin_layout Section
\begin_inset LatexCommand label
name "sec:recompile"

\end_inset

Recompiling
\end_layout

\begin_layout Standard
Note, that most watermark embedding/extraction programs use the built-in
 random number generator of the C library, i.e.
 
\family typewriter
\size small
srandom()
\family default
\size default
 and 
\family typewriter
\size small
random().

\family default
 
\size default
Therefore, if you recompile, chances are that you won't be able to use your
 images watermarked with the previous version.
\end_layout

\begin_layout Standard
The Makefile options for compiling on the different platforms can be found
 in the 
\family typewriter
\size small
make/
\family default
\size default
 sub-directory of the archive.
\end_layout

\begin_layout Subsection
\begin_inset LatexCommand label
name "sec:prereq"

\end_inset

Prerequisites
\end_layout

\begin_layout Subsubsection
NetPBM
\end_layout

\begin_layout Standard
NetPBM is responsible for image file I/O and provides a definition of a
 simple image file format along with many image file format filters that
 allow to convert images to and from NetPBM format.
 
\end_layout

\begin_layout Standard
You need to get and install the NetPBM library at 
\begin_inset LatexCommand url
target "http://wuarchive.wustl.edu/graphics/graphics/packages/NetPBM/"

\end_inset

 or 
\begin_inset LatexCommand url
target "http://netpbm.sourceforge.net"

\end_inset

.
 The library provides 
\family typewriter
\size small
pgm.h
\family default
\size default
 and the appropriate implementation.
\end_layout

\begin_layout Subsubsection
getopt
\end_layout

\begin_layout Standard
When compiling on Windows, the getopt() function call required.
 An implementation of getopt() can be found in the NetPBM package.
 
\end_layout

\begin_layout Subsection
Unix/Linux platform
\end_layout

\begin_layout Standard
All programs were developed using Linux and GNU C.
 The programs should compile and work with all recent versions of Linux
 and GNU C.
 
\end_layout

\begin_layout Subsection
\begin_inset LatexCommand label
name "sec:win32_compile"

\end_inset

Win32 platform
\end_layout

\begin_layout Standard
The programs were ported to the Windows platform using the Cygwin
\begin_inset Foot
status collapsed

\begin_layout Standard
\begin_inset LatexCommand url
target "http://www.cygwin.com"

\end_inset

 
\end_layout

\end_inset

and Mingw
\begin_inset Foot
status collapsed

\begin_layout Standard
\begin_inset LatexCommand url
target "http://www.mingw.org"

\end_inset


\end_layout

\end_inset

 environment.
 Most notable, the file mode for standard input and standard output has
 to be set to binary mode.
 This is accomplished with the 
\family typewriter
\size small
setmode()
\family default
\size default
 or 
\family typewriter
\size small
_fsetmode()
\family default
\size default
 commands.
\end_layout

\begin_layout Section
FAQ
\end_layout

\begin_layout Standard
Q: How can I report problems?
\end_layout

\begin_layout Standard
A: See the contact information at the beginning of this document.
\end_layout

\begin_layout Standard
Q: The compiler complains about 
\family typewriter
\size small
pgm.h
\family default
\size default
?
\end_layout

\begin_layout Standard
A: You need to get and install the NetPBM library, see section 
\begin_inset LatexCommand ref
reference "sec:prereq"

\end_inset

.
\end_layout

\begin_layout Standard
Q: What is the best algorithm? 
\end_layout

\begin_layout Standard
A: Depends on your application.
\end_layout

\begin_layout Standard
Q: What is the most robust algorithm?
\end_layout

\begin_layout Standard
A: Depends on the attack.
 See some results on 
\begin_inset LatexCommand url
target "http://www.cosy.sbg.ac.at/~pmeerw/Watermarking"

\end_inset

.
\end_layout

\begin_layout Standard
Q: I need code for a full-frame DCT?
\end_layout

\begin_layout Standard
A: See the files Meerwald/dct.* in the archive.
\end_layout

\begin_layout Standard
Q: I need code for a 8x8 block DCT?
\end_layout

\begin_layout Standard
A: See the files 
\family typewriter
\size small
Meerwald/dct.*
\family default
\size default
 in the archive.
\end_layout

\begin_layout Standard
Q: I need code for the wavelet transform (DWT)?
\end_layout

\begin_layout Standard
A: See the files 
\family typewriter
\size small
Meerwald/wavelet.*
\family default
\size default
 in the archive.
\end_layout

\begin_layout Standard
Q: I get the message 'unable to open filter.dat' - what to do?
\end_layout

\begin_layout Standard
A: Make sure the file filter.dat is in the current directory or accessible
 via path/filename specified in the signature file.
 Use the signature generation command to specify an absolute path if necessary.
\end_layout

\begin_layout Standard
Q: I can't compile the code using some Microsoft product?
\end_layout

\begin_layout Standard
A: Make your life easier, install GNU software! See section 
\begin_inset LatexCommand ref
reference "sec:recompile"

\end_inset

.
\end_layout

\begin_layout Section
Revision history
\end_layout

\begin_layout Standard
version 0.5 (December, 2005)
\end_layout

\begin_layout Itemize
added algorithm kund3, kund2 and xie2
\end_layout

\begin_layout Standard
version 0.4 (June 21, 2001)
\end_layout

\begin_layout Itemize
bug fixes 
\end_layout

\begin_deeper
\begin_layout Itemize
wm_xia_{e|d}.c variable level uninitialized 
\end_layout

\begin_layout Itemize
wm_zhu_{e|d}.c variable level uninitialized
\end_layout

\begin_layout Itemize
issue with random() vs.
 rand() and RAND_MAX in frid2_common.c
\end_layout

\end_deeper
\begin_layout Itemize
added option to bruyn algorithm to disable block skipping
\end_layout

\begin_layout Itemize
added algorithm kim
\end_layout

\begin_layout Standard
version 0.3 (June 18, 2001)
\end_layout

\begin_layout Itemize
created a nice (?) manual/documentation
\end_layout

\begin_layout Itemize
added algorithms by Dugad, Wang, Zhu, Fridrich
\end_layout

\begin_layout Itemize
added Makefiles for Win32 platform (mingw32)
\end_layout

\begin_layout Standard
version 0.2 (February 22, 2001)
\end_layout

\begin_layout Itemize
added contribution by Vassilis Fotopoulos (Piva's algorithm,
\end_layout

\begin_layout Itemize
DCT, Hartley and subband domain) - see Fotopoulos/ subdirectory
\end_layout

\begin_layout Itemize
stuff moved to Meerwald/ subdirectory
\end_layout

\begin_layout Itemize
added Bruyndonckx, Corvi, Koch, Xia, Xie algorithms
\end_layout

\begin_layout Standard
version 0.1 (February 18, 2001)
\end_layout

\begin_layout Itemize
initial release
\end_layout

\begin_layout Section
Legal statement
\end_layout

\begin_layout Standard
My license is called "I-don't-care" license: (1) You can do with the accompanyin
g software whatever you want, but don't blame me if it doesn't work or it
 causes damage.
 (2) If you think my work is useful, tell me and tell others, but you are
 not obliged to do so.
 I suggest not to remove information contained in this other documentation
 file.
\end_layout

\begin_layout Standard
\begin_inset LatexCommand bibtex
options "plain"
bibfiles "watermarking"

\end_inset


\end_layout

\end_body
\end_document