The priority of RFID is that it does not require direct contact or line-of-sight scanning. An RFID system consists of three elements: an antenna and transceiver (often combined into a single reader) and a transponder (the tag). The antenna uses radio frequency waves to transmit a signal that activates the transponder. When activated, the tag transmits data to the antenna. The data is used to inform a programmable controller that an action should occur. The action can be as simple as opening an access door or as complicated as interfacing with a database to perform a monetary transaction. Low frequency RFID systems (30 KHz to 500 KHz) have short transmission ranges (typically less than six feet). High-frequency RFID systems (850 MHz to 950 MHz and 2.4 GHz to 2.5 GHz) offer longer transmission ranges (over 90 feet). In general, the higher the frequency, the more expensive the system. RFID is sometimes called dedicated short-range communication (DSRC).28.2 Introduction to RFIDWith all the potential doomsday scenarios that critics like to associate with the use of RFID systems, why would anyone consider doing so? Indeed, RFID systems offer three distinct advantages over traditional identification systems:1. Automation. While optical barcodes require line of sight for reading, meaning either careful orientation of the tagged goods relative to the reader or manual intervention, RFID tags promise unsupervised readings. This increases the level of automation possible, as labeled items do not need precise orientation during the reading process.2. Identification. RFID tags also offer a much higher information density than barcodes, allowing manufacturers and sellers to not only store a generic product identifier...... middle of paper...... l ID) to unlock it again. However, as a single fixed meta-id would not solve the problem of location privacy, i.e. unwanted tracking and profiling, these meta-ids would have to change periodically, e.g. on every read request . But with an ever-changing ID, even legitimate readers might struggle to find a tag's correct password in order to unlock it. This implies the need for large data management structures to keep track of its articles and their current meta-identifiers – a requirement which calls into question the practicability of such a system. Even if one assumes a single password for all one's personal items (e.g. a smartphone provides a key to the supermarket's point-of-sale device during checkout), the associated key management problem would still be significant (imagine buying things for others). people, or forgetting your phone at home).