Encrypted QR codes for Android
I just came across an interesting application that's available for Android devices. This particular app let's you create and read encrypted QR (quick response) codes.
QR codes are those images that you see that look something like this:
These were created by Toyota back in 1994 to help track vehicles while they were begin manufactured, but now they're widely used in cell phones and other portable devices. Just take a picture of the QR code and many portable devices can easily translate that picture into a URL, phone number, or whatever was encoded in it. If you're really interested in how these work, you can find out in ISO/IEC 18004:2006 ("Information technology — Automatic identification and data capture techniques — QR Code 2005 bar code symbology specification").
The good thing about QR codes is that they're a standard, so anyone with a standards-compliant device can read one. But that also means that there's no privacy for information in QR codes because anyone with a standard-compliant device can read one. One workaround for this is to encrypt the data in a QR code, and that's just what QR Droid lets you do. It uses password-based encryption, so a typical use might be to encrypt those potentially-compromising pictures that you post on Facebook and to only share the password with your friends, thereby keeping any nosy HR people from blackballing you from future jobs because of what you did on your vacation to Cozumel.
Password-based encryption isn't very secure, of course, but it might be secure enough to protect the privacy of what you post on Facebook. If that's what you need, then QR Droid might be just what you're looking for.