---
name: "snowdrop"
section: "1"
platform: "linux"
package: "snowdrop"
version: "0.02b-12.1+b2"
release: "Debian 10 (Buster)"
platforms: ["linux"]
url: "https://new.carta.tech/snowdrop"
---

# snowdrop(1)

text watermarking and watermark recovery

## 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.

## FILES

- **~/.snowdrop/database**

  Database of watermarked files.

## SEE ALSO

- **/usr/share/doc/snowdrop/README.gz**

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

## AUTHOR

Michal Zalewski \<lcamtuf@coredump.cx\>