Your communications are being monitored by employers, third party services, and prying eyes. As privacy continues to be obstructed and impeded upon, users will find alternative methods of communicating to avoid being monitored.

To hide the existence of data from a third party we can use a covert communication art known as steganography. Steganography is the practice of concealing data by embedding it within other data, such as audio, video, or an image file. The difference between steganography and encryption is that only the sender and recipient know that there is hidden data.

In this tutorial you will learn how to conceal data in an image, and then learn how to extract that same hidden data from the image.

For this tutorial we will be using the open-source program Steghide.

Install Steghide from the terminal in Linux.

sudo apt-get install steghide

Use the --help flag to view options available for Steghide.

steghide --help

Steghide requires a command that tells the tool what action to perform.

steghide {embed/extract/info} [arguments]

We are going to use the image below to conceal a message. Save the image to your machine.

Create a text file with the following message:

echo "The quieter you become, the more you can hear." > secret.txt

Now that we have an image to conceal our message we can embed the file within the image.

steghide embed -ef <PATH/TO/EMBED/FILE> -cf <PATH/TO/COVER/FILE>

This command will embed the file secret.txt in the cover file car.jpg.

steghide embed -ef secret.txt -cf car.jpg

You will be prompted to enter a password to secure the encoded file. Try using the passphrase Pa$$w0rd.

Enter a passphrase:
Re-Enter passphrase:

steghide extract -sf </PATH/TO/FILE> -p [password] -xf <PATH/TO/NEW/FILE>

steghide extract -sf cat.jpg -p Pa$$w0rd -xf message.txt

Enter the passphrase you used to secure the encoded file.

Enter a passphrase: 
Re-Enter passphrase:

Practice communicating using steganography by sharing this tutorial with someone. Take your covert communication skills further by sharing the passphrase to steganographic files over a secure, offline communication channel.