/outguess

Universal steganographic tool

Primary LanguageC

OutGuess 0.2.1

2018-11-11 - Joao Eriberto Mota Filho eriberto@eriberto.pro.br,

fully based on OutGuess 0.2, by

2001-02-12 - Niels Provos provos@citi.umich.edu

OutGuess is a universal steganographic tool that allows the insertion of hidden information into the redundant bits of data sources. The nature of the data source is irrelevant to the core of OutGuess. The program relies on data specific handlers that will extract redundant bits and write them back after modification. In this version the PNM and JPEG image formats are supported. In the next paragraphs, images will be used as concrete example of data objects, though OutGuess can use any kind of data, as long as a handler is provided.

OutGuess is available under the BSD software license. It is completely free for any use including commercial.

Please see each source file for its respective license. OutGuess was developed in Germany.

Steganography is the art and science of hiding that communication is happening. Classical steganography systems depend on keeping the encoding system secret, but modern steganography are detectable only if secret information is known, e.g. a secret key. Because of their invasive nature steganography systems leave detectable traces within a medium's characteristics. This allows an eavesdropper to detect media that has been modified, revealing that secret communication is taking place. Although the secrecy of the information is not degraded, its hidden nature is revealed, defeating the main purpose of Steganography.

For JPEG images, OutGuess preserves statistics based on frequency counts. As a result, no known statistical test is able to detect the presence of steganographic content. Before embedding data into an image, the OutGuess system can determine the maximum message size that can be hidden while still being able to maintain statistics based on frequency counts.

OutGuess uses a generic iterator object to select which bits in the data should be modified. A seed can be used to modify the behavior of the iterator. It is embedded in the data along with the rest of the message. By altering the seed, OutGuess tries to find a sequence of bits that minimizes the number of changes in the data that have to be made.

A sample output from OutGuess is as follows:

Reading dscf0001.jpg....
JPEG compression quality set to 75
Extracting usable bits: 40059 bits
Correctable message size: 21194 bits, 52.91%
Encoded 'snark.bz2': 14712 bits, 1839 bytes
Finding best embedding...
    0:  7467(50.6%)[50.8%], bias  8137(1.09), saved:   -13, total: 18.64%
    1:  7311(49.6%)[49.7%], bias  8079(1.11), saved:     5, total: 18.25%
    4:  7250(49.2%)[49.3%], bias  7906(1.09), saved:    13, total: 18.10%
   59:  7225(49.0%)[49.1%], bias  7889(1.09), saved:    16, total: 18.04%
59, 7225: Embedding data: 14712 in 40059
Bits embedded: 14744, changed: 7225(49.0%)[49.1%], bias: 7889, tot: 40032, skip: 25288
Foiling statistics: corrections: 2590, failed: 1, offset: 122.585494 +- 239.664983
Total bits changed: 15114 (change 7225 + bias 7889)
Storing bitmap into data...
Writing foil/dscf0001.jpg....

The simple example script seek_script uses OutGuess to select an image that fits the data we want to hide the best, yielding the lowest number of changed bits. Because we do not care about the actual content of the cover data we send, this is a very viable approach.

Additionally, OutGuess allows to hide multiple messages in the data. Thus, it also provides plausible deniability. It keeps track of the bits that have been modified previously and locks them. A (23,12,7) Golay code is used for error correction to tolerate collisions on locked bits. Artificial errors are introduced to avoid modifying bits that have a high bias.

This version of OutGuess can insert only two different messages. As this is a BETA version, I would like you to give me feedback on the usefulness of OutGuess. And if you like it, you can support me via the links on

http://www.outguess.org/

Note, by Eriberto: all text shown here was originally written by Niels Provos for OutGuess =< 0.2. The current site for OutGuess is:

https://github.com/eribertomota/outguess

Installation

Prepare the jpeg-6b-steg library

To do so, you need to choose (and potentially edit) an appropriate jconfig.h file.

To get an idea which one you might want, have a look at their header comments.

You might do so like this (POSIX only):

head -n 1 jpeg-6b-steg/jconfig.*

The default one is jconfig.cfg. You may use it like this:

cd jpeg-6b-steg
ln -s jconfig.cfg jconfig.h
cd ..

Build OutGuess

OutGuess has only been tested on OpenBSD, Linux, Solaris and AIX.

Supported Systems

OutGuess has been modified to use autoconf. A normal installation should require only:

  1. ./configure && make

There is an optimization bug in gcc, so you might have to compile with -O0.

Unsupported Systems

If your system is not supported, try building by hand as follows:

  1. Install the JPEG-6b libjpeg.a library and patch it with jpeg-6b-steg.diff. You can obtain the source from ftp://ftp.uu.net/graphics/jpeg/jpegsrc.v6b.tar.gz. The Makefile expects the library to be at ../jpeg-6b.

    NOTE (by Eriberto)
    Currently, the jpeg-6b can be found at
    https://www.ijg.org/files/

  2. Edit the Makefile and type make

BUGS

None known at the moment.

You may want to check the code from time to time with a static code checker like CppCheck:

cppcheck --enable=all *.c &> cppcheck_log.txt
less cppcheck_log.txt

Acknowledgments

OutGuess uses code from the following projects. Attributions can also be found in the sources.

For determining the redundant bits out of a JPEG image, the jpeg-jsteg-v4 patches by Derek Upham upham@cs.ubc.ca were helpful.

Thanks to: