---
name: "outguess-extract"
section: "1"
platform: "linux"
package: "outguess"
version: "1:0.4-2"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/outguess"
---

# outguess-extract(1)

universal steganographic tool

Part of [outguess(1)](/outguess/1.md).

## NAME

**outguess** - universal steganographic tool

## SYNOPSIS

```
 outguess [OPTIONS] inputfile outputfile
```

## DESCRIPTION

**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. Currently only the PPM, PNM, and JPEG image formats are** **supported, although OutGuess could use any kind of data, as long as a handler** **were provided.**

**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 bias is introduced that favors the modification of bits that were extracted** **from a high value, and tries to avoid the modification of bits that were** **extracted from a low value.**

**Additionally, OutGuess allows for the hiding of two distinct messages in the** **data, thus providing 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.**

## OPTIONS

**The following command line options, when specified as capital letters,** **indicate options for the second message.**

- **-F \[+-\]**

  **Specifies that OutGuess should preserve statistics based on** **frequency counts. As a result, no statistical test that is** **based on frequency counts will be able to detect** **steganographic content. This option is set as on by default.**

- **-kK \<key\>**

  **Specify the secret key used to encrypt and hide the message in** **the provided data.**

- **-dD \<datafile\>**

  **Specify the filename containing a message to be hidden in the** **data.**

- **-sS \<seed\>**

  **Specify the initial seed the iterator object uses for selecting** **bits in the redundant data. If no upper limit is specified, the** **iterator will use this seed without searching for a more** **optimal embedding.**

- **-iI \<limit\>**

  **Specify the upper limit for finding an optimal iterator seed.** **The maximum value for the limit is 65535.**

- **-eE**

  **Use error correction for data encoding and decoding.**

**Other options that apply to the general execution of OutGuess:**

- **-r**

  **Retrieve a message from a data object. If this option is not** **specified, OutGuess will embed messages.**

- **-x \<maxkeys\>**

  **If the second key does not create an iterator object that is** **successful in embedding the data, the program will derive up to** **specified number of new keys.**

- **-p param**

  **Passes a string as parameter to the destination data handler.** **For the JPEG image format, this is the compression quality, it** **can take values between 75 and 100. The higher the quality the** **more bits to hide a message in the data are available.**

- **-m**

  **Mark pixels that have been modified.**

- **-t**

  **Collect statistics about redundant bit usage. Repeated use** **increases output level.**

- **-h**

  **Print a usage help text and exit.**

**For embedding messages, you need to specify a source and a destination** **filename. OutGuess determines the data format by the filename extension. If no** **filenames are specified OutGuess operates as a filter and assumes the PPM data** **format.**

## EXAMPLES

**To embed the message hidden.txt into the monkey.jpg image:**

```
    $ outguess -k "my secret pass phrase" -d hidden.txt monkey.jpg out.jpg
```

**And in the other direction:**

```
    $ outguess -k "my secret pass phrase" -r out.jpg message.txt
```

**will retrieve the hidden message from the image.**

**If you want to embed a second message, use:**

```
    $ outguess -k "secret1" -d hide1.txt -E -K "secret2" -D hide2.txt monkey.jpg out.jpg
```

**OutGuess will first embed hide1.txt and then hide2.txt on top of it, using** **error correcting codes. The second message hide2.txt can be retrieved with**

```
    $ outguess -k "secret2" -e -r out.jpg message.txt
```

## SEE ALSO

**[cjpeg(1)](/cjpeg/1.md), [djpeg(1)](/djpeg/1.md), [pnm(5)](/pnm/5.md), [seek\_script(1)](/seek_script/1.md), stirmark(1)**

## AUTHOR

**OutGuess was originally developed by Niels Provos \<provos@citi.umich.edu\> and** **is maintained by some people.**

**Currently, source code and newer versions are available at** **https://github.com/resurrecting-open-source-projects/outguess**