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Langue: en

Version: 257070 (debian - 07/07/09)

Section: 1 (Commandes utilisateur)


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


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

sd-eng [-6] -e origfile newfile

sd-eng [-6] -l


snowdrop is a stenographic text watermarking and watermark recovery system. It is composed of three programs:
Watermark normal English text.
Watermark fine quality English text, yeilding higher quality output but encoding less information.
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.


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.
Extract a watermark from a file. Needs the original file and the new file that you suspect bears the watermark.
Lists the contents of the watermark database. Each of the three programs will have a different list.
Enable 64 bit waterarking. The default is a weak 32 bit watermark.


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


Database of watermarked files.


Explain snowdrop in more depth, its limitations, and how to write additional watermarking modules for other tpyes of files.


Michal Zalewski <>
Je n'aime pas travailler, mais j'admets que les autres travaillent.
-+- Arthur Adamov (1908-1970) -+-