Masabi's Ben Whitaker wrote a most interesting article on Barcode security. Even those readers who don't usually care about such things should have a look; lots of interesting ideas there. Whitaker addresses security and DRM:
Anti-copying using DRM (Digital Rights Management)
However you deliver a barcode, it has to be presented in a scannable format, which means that an adversary can always scan the ticket, and if they want to, change some details on the barcode and create multiple copies without DRM. People that have barcode delivery systems that use or rely on "forward lock" or DRM to prevent the barcode image being sent from one person to another are being blind to the availability of barcode scanners to beat all of their software. Also consider that OMA DRM for forward locking images downloaded to phones places laughably little protection against an assailant armed with such exotic tools as a web-browser and a text editor.