Steganography and Linux: A short steghide howto

December 27, 2007

Here I will how to hide a file, encrypted and passwordprotected in anonther file, for example a picture.

First you have to install “steghide”, use synaptic or whatever you want…

Steghide can use *.bmp,*.jpg, *.wav und *.au-files to hide data. I would recommend *.jpg, because all the other formats are quite unusual today in most pc-enviremonts(you want send a friend a song in *.wav-format and you certainly do not store your holiday pictures as *.bmps…)

To hide a file you use this command in the terminal(there is no gui for steghide):

steghide embed -cf picture.jpg -ef secrettext.txt

Of course you have to give the path to both files, so an example would be:

steghide embed -cf /home/usr/pictures/picture.jpg -ef /home/usr/secrettext.txt

Now steghide will ask you for a password and then embed the file secrettext.txt in the file picture.jpg. And it will encrypt the file with AES, so if you do not know the password you just will not know that there is any file stored in the picture…

Then you just get the message(sry for german):

steghide: Mit diesem Passwort konnten keine Daten extrahiert werden!
(With this password no data could be extracted)

Of course the size of the file you can store in another file is limited, if you just want to know how big the file can be, enter:

steghide info picture.jpg

(of course yo have, as said above, to give the path, so for example steghide info /home/usr/pictures/picture.jpg)

and steghide will tell you the maximum filze size!

With the command

steghide extract -sf picture.jpg

you get all your data back, just enter your password and the hidden file will be stored in the same folder as the picture…

Update: If this howto is not working for you, you probably have to use sudo in front of all commands! Or sudo -i as the first command, so you get sudo(admin)-rights for everything you enter in this terminal…

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