What is the security concept in printer cartridge? Based on this datasheet or this patent, one of the usage of PUF is printer cartridge identification and authentication. I was wondering why printer cartridge needs identification and authentication. In other words, what is the security concept behind it?

Furthermore, 

what is the required protocol for it? 

which item behaves as PUF? 

who sends the challenge? 

who verifies the correctness of the response for the given challenge?
A company can make more money if the printers it sells only work with the cartridges they sell, which does not work if there is competition. It's cheaper to force a vendor lock-in than it is to innovate and ensure that your product holds up to the competition. All the printer's authentication does is prevent you from using cartridges made by other companies. Think of it like DRM for ink. It's just capitalism.

There is no standard protocol. Each vendor is free to implement this in their own way. Most likely it's some form of challenge-response authentication done between the cartridge and the printer.