SNOWDROP(1)						      General Commands Manual						       SNOWDROP(1)

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, yeilding 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 man-
       gling, etc.

       The watermark is a md5sum, which is retreivable 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 redundently in multiple independent channels.

       The three usage modes are adding a watermark, checking for the presense of a watermark, and listing the contents of your database of water-
       marks. 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 watwrmarked 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/snowdrop/README
	      Explain snowdrop in more depth, its limitations, and how to write additional watermarking modules for other tpyes of files.

AUTHOR

       Michal Zalewski <lcamtuf@coredump.cx>

																       SNOWDROP(1)