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
mangling, 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 independant channels.
The three usage modes are adding a watermark, checking for the presense
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 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 waterarking. 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>