Can you point me to an opensource implementation of an encrypted qr code similar to what quickmark is doing? check this out:
http://www.quickmark.com.tw/En/diy/?qrEncrypt
If possible, an implementation that works on both mobile and pc applications.
Here is a quick explanation on how QuickMark works http://uvsar.blogspot.com/2009/05/secure-qr-and-qm-codes.html
They appear to be simply encoding the encrypted data as a URL with the prefix 'pe:', followed by the raw encrypted data. There isn't a standard for this, so you can do it however you want, really. Are you trying to make something compatible with their system? If not, what are your requirements? I'm finding it hard to understand why you'd want an encrypted QR code.