sd-eng, sd-engf, sd-c - text watermarking and watermark recovery
SYNOPSIS
sd-eng [-6] -iorigfilenewfileRecipient [Comment]
sd-eng [-6] -eorigfilenewfile
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.