PKA, Partial Knowledge-based Access, is a Firefox-extension which allows you to encrypt your Facebook data, so that only your friends can access it without exchanging keys and other annoying overheads. Simply select a couple of attributes about your, for example the name of your pet, your birthday and your current employee, and restrict access to people, knowing at least two of these attributes. To use PKA, download it from the following link
and install it by drag&drop in your browser. After installation, you need to restart your browser to see the PKA logo in the Add-on toolbar in the lower right corner of your browser window (in case the Add-on toolbar is not activated, click 'View->Toolbars' and check Add-on bar) as can be seen in Figure 1. Open the menu by right-clicking the logo.
You can now publish and access encrypted Facebook notes. Before publishing your first note, you need to choose personal attributes as, e.g. nickname. First, electing 'Information Manager' in the menu. Here you can enter a description for your attribute, e.g. nickname, and the corresponding value, e.g. 'Smurf'. For actually publishing a note, choose 'Create Note', enter your message, as well as a title, and decide on the attributes for protection as well as the Quorum, the number values that your friends have to know to access the message (see Figure 2). You have be logged in to Facebook for publishing a note. If it is the first note you want to publish, you need to give a corresponding Facebook App the right to publish Facebook notes.
Figure 2: Create Note
When accessing a friends encrypted messages, browse to a page of their Facebook profile, e.g. Timeline, Notes. Then simply choose 'Decrypt Note'. A dialogue opens: Here you can choose which node to decrypt. You are given some questions about your friend. After answering a certain amount of them correctly, your friend's message is displayed in the corresponding field (see Figure 3).
Figure 3: Decrypt Note
Please note that all information is stored only on your local machine, so nobody, including Facebook and us as the extension provider, can access your chosen values.
PKA was implemented by Manuel Hauptmann, with the help of Stefanie Roos, Benjamin Schiller, Frederik Armknecht and Thorsten Strufe.
Manuel Hauptmann (mhauptma(a-t)mail.uni-mannheim.de)
Stefanie Roos (roos(a-t)cs.tu-darmstadt.de)