The privacy issues raised by radio-frequency identification (RFID) technology have been widely dealt within the state of the art and numerous solutions have been developed. The main drawback of proposed security solutions is often the fact that they entail nonnegligible costs, first in terms of memory and computation capacity for the RFID tag, and second in terms of computations amount for the back-end database to identify the tag. These cost restrict the potential of large-scale deployment of secure RFID tags. This chapter examines the privacy protecting schemes that aspire to limit these constraints for the different entities of the RFID system. It first introduces the scalability problems that privacy protecting schemes may lead to. Then, it presents the different categories of solutions with their strengths and weaknesses, such as protocols based on cryptanalytical techniques, privacy protecting schemes with synchronization between the RFID tags and the back-end database, and finally solutions based on temporary or even permanent delegation to trusted readers