Consider an RFID authentication system used in a clothing retail store, where readers send challenges to tags. Challenges are random strings, and tags are wireless transponders that respond to the challenges. Each tag has a unique identifying string Id. The system can be used in two modes: scanning mode (used for taking inventory) and individual mode (used for determining prices during checkout). In a scanning mode a reader broadcasts a challenge, and all tags in a short range from the reader will receive the same challenge and respond. Under individual mode, a tag will receive an individual challenge and will respond with its Id, which will be used to determine the price that the customer must pay. Consider an RFID authentication system used in a clothing retail store, where readers send challenges to tags. Challenges are random strings, and tags are wireless transponders that respond to the challenges. Each tag has a unique identifying string Id. The system can be used in two modes: scanning mode (used for taking inventory) and individual mode (used for determining prices during checkout). In a scanning mode a reader broadcasts a challenge, and all tags in a short range from the reader will receive the same challenge and respond. Under individual mode, a tag will receive an individual challenge and will respond with its Id, which will be used to determine the price that the customer must pay