NAME

       sd-eng, sd-engf, sd-c - text watermarking and watermark recovery

SYNOPSIS

       sd-eng [-6] -i origfile newfile "Recipient" ["Comment"]

       sd-eng [-6] -e origfile newfile

       sd-eng [-6] -l

DESCRIPTION

       snowdrop  is  a  stenographic  text  watermarking and watermark recovery system.  It is composed of three
       programs:

       sd-eng Watermark normal English text.

       sd-engf
              Watermark fine quality English text, yielding higher quality output but encoding less information.

       sd-c   Watermark C code.

       The three programs operate similarly, with the same parameters and usage.  The watermark  is  encoded  in
       using  a  number  of  techniques,  such as whitespace reformatting, typo insertation, word substitutions,
       punctuation changes, and for C code, logic reordering, variable name mangling, etc.

       The watermark is a md5sum, which is retrievable from as little as  5  or  10  lines  of  the  watermarked
       document. Even large changes to a medium sized document should not obscure the watermark, as it is stored
       redundantly in multiple independent channels.

       The three usage modes are adding a watermark, checking for the presence of a watermark, and  listing  the
       contents  of your database of watermarks. Note that to later check a watermark, you must retain a copy of
       the original, un-watermarked file.

OPTIONS

       -i     Inject a watermark into a file. You must pass it the original file, the  filename  to  output  the
              watermarked version to, information about who you intend the watermarked file for, and an optional
              comment.

       -e     Extract a watermark from a file. Needs the original file and the new file that you  suspect  bears
              the watermark.

       -l     Lists  the  contents  of  the watermark database. Each of the three programs will have a different
              list.

       -6     Enable 64 bit watermarking. The default is a weak 32 bit watermark.

ENVIRONMENT

       SD_SYNONYMS
              This variable can be used to point snowdrop at a customized synonyms file.

FILES

       ~/.snowdrop/database
              Database of watermarked files.

SEE ALSO

       /usr/share/doc/snowdrop/README.gz
              Explain snowdrop in more depth, its limitations, and how to write additional watermarking  modules
              for other types of files.

AUTHOR

       Michal Zalewski <lcamtuf@coredump.cx>

                                                                                                     SNOWDROP(1)