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  steganographic  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)