Is the any QR code with built-in hash of the information?
There are encrypted QR codes from DENSO ADC.  I know that these can be encrypted or just signed; however, DENSO ADC has never been forthcoming with how they work.  They seem to work by putting data after the "data section" of the QR code that would otherwise be ignored.  If you were going to have something similar, I would take that approach.