Top Secret #3 : Printable secrets

Digital data remains the most secure media.

Nevertheless, some situations would require to keep a secret phrase or any secret code onto a physical media.

No internet, lack of energy or any climatic event would lead to a more or less long off-grid time period, preventing you to access a cloud service.

Worst, a cloud service could be damaged due to these events and there is no guarantee that your data would be backuped.

A poster, a paper, a letter, a drawing or some other printable media can embbed short secrets.

Here is an example with a photo of a beach :

Perhaps you can see some little lines and crosses on this photo. These are the encoded bits.

This image encodes 1 text file named "readme.txt" containing the text "my secret data".

If you print this image on an A4 page at 300 DPI (dots per inch) and scan it back again at 300 DPI, the original rectangular image would be precisely located on the full A4 scanned image and the secret decoded.

To use this implementation, you'll have to download the PaperSecret plugin.

Put the SecretPaper.jar file in the same directory where the TopSecret.jar file is :

Run TopSecret and that's all ! The plugin will be automatically detected and loaded.

PaperSecret adds 1 codec (Coder / Decoder) into the main application : Paper/1

The "/1" stands for the codec version. Any future improvement will keep the previous implementation versions to allow older encoded secrets to remain decodable.

The encoding section presents the codecs and the output format :

Please note the the PaperSecret output encoder only exports PNG file (i.e. no JPEG) to avoid any distortions before printing.

Enjoy !