I need to hand out physical access cards to a group of people. My main objective is to guarantee at every location where this cards will be checked that no information in the card has been modified. I print those cards so I have all the user information (name, lastname, ID number, etc).
My idea is to use some sort of algorithm to input all this data and generate a maximum of 15-20 digit barcode that I can print in the card.
The cards will be checked using scanners similar to those used for passport control, which means that the operator will have the ability to obtain all the information in the card by OCR. Without distributing my input algorithm (and risking someone else being able to replicate it), is there a way to have him check that no information has been modified on the card?
I'm open to all suggestions regarding my need as nothing is implemented yet. However, I cannot connect the verification points with a central server for checking, they are remote locations with no internet. The cards should hold data on themselves that allows to verify that no data has been modified. The cards don't have chips or magnetic stripe, so I'm locked to using OCR.
Thanks in advance!