RFID technology is widely used worldwide in a broad range of applications. Such technology however raises security concerns about the protection of the information stored in the RFID tags and exchanged during the wireless communication with the readers. In this work we propose an efficient protocol for tag identification which improves on previous proposals and provides an increased level of security, allowing??dynamic addition or remotion of tags from the set of recognized tags. The protocol relies on the use of skip lists, authenticated data structures previously used in other fields of application.