This Technical Report provides guidance to systems designers to help them determine potential threats to data security of the tag and tag-to-reader communication in an RFID system, and appropriate countermeasures to provide data security (identified as 1 through 2 in Figure 1). Although important, it is beyond the scope of this Technical Report to address security aspects of the reader-to-host and back-end enterprise modules (identified as 4 through 7 in Figure 1).1)This Technical Report is not intended to specifically address consumer privacy concerns; however, since data and personal privacy depend on the use of appropriate security measures, privacy is a