sd-engf - Online in the Cloud

PROGRAM:

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, 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.

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