A 21-year-old student has a Chrome extension released, which is a simple way secret messages can be hidden in photos on Facebook. That was until now difficult because of the compression that Facebook applies to pictures.
The student at the university of Oxford in the United Kingdom for the development of the extension determined how Facebook photos compresses and its findings published. The extension with the name Secretbook put the message a number of times in the image, so the algorithm is always the secret message should be able to figure it out.
The technology works by a couple of pixels according to a fixed pattern subtle color change. Secretbook works best on images with lots of detail; the extension warns no pictures to use with large sections of blue sky, because the method is less good works. The lower the resolution of the image is, the shorter is the message that can be sent.
The app works by, after installation, on Facebook, the key combination Ctrl-Shift-A to use, and then in a window of the message, a password and a picture can be selected. The picture with the message is then downloaded, and has a name like DSC0165.jpg which makes it seem as if the of a camera. That picture can then be uploaded.
The receiver message can decrypt it by installing the application, then clicking on the image, and then also Ctrl-Shift-A key. Therefore, a window appears which prompt for a password. If that is correct, the message in a dialog box.
The creator, Owen Campbell More, makes a number of reservations in the terms and conditions: this provides the file extension does not ‘military grade’ encryption and should not be used for terrorist purposes. The extension does not work through a Facebook app, but with an extension that can be called on any page on Facebook. As a result, the application is not subject to the approval of Facebook. Because the extension only local spins, can network analysis do not reveal whether a user of the extension used.
Embedding messages in images is not new: on Google+, for example, always already, because Google no further compression on the uploads. Also in other communication channels, this form of steganography already known much longer. It is not known whether there are other roundabout ways to secret messages in Facebook pictures to stop.
