# 5G-Compliant Authentication Protocol for RFID
## 1 Introduction  
Cellular network technologies have evolved from 1G, that supported radio communications, through voice-only 2G technology and 3G networks, supporting Internet connections, to the faster and mostly used currently 4G. The standards of the two latter technologies, 3G and 4G, have been designed by the 3 GPP consortium. This consortium has also been working to develop their successor 5G, which aims not just to be faster and more reliable, but also to become the key enabler to support the next generation wireless communications. Moreover, 5G aims to realize the \"Internet of Everything\" and thus, it is designed to support three main services: enhanced mobile broadband (eMBB), massive machine type communications (mMTC) and ultra-reliable and low latency communications (uRLLC). Nevertheless, some privacy issues detected in prior generations have increased the distrust in this new technology, and its security has become a crucial aspect that could derail, or at least delay, its imminent deployment.  
On the other hand, radio frequency identification (RFID) is a widely deployed technology for supply chain management, inventory, retail operations and more generally automatic identification. A typical RFID deployment has three main components: tags or transponders, which are electronicdata storage devices attached to (or embedded in) objects to be identified; readers or interrogators, that manage tag population, read data from and write data to tags; and back-end servers, which exchange information with the readers and processes data according to specific task applications. Although the term \"Internet of Things\" (IoT) currently encompasses a myriad of medium/small devices connected to the Internet, it was originally coined in 1999, when RFID technology was being developed, to refer to applications where RFID-tagged objects and sensors enabled computers to achieve effective situational awareness without human intervention [1].  
Surprisingly, despite the importance of RFID for the development of the IoT, and the fact that, as mentioned, 5G provides the mMTC service which improves the existing NB-IoT and LTE-M services introduced in 2015, RFID technology has not found its own space within mobile networks, and its integration is not as one would expect, considering RFID tags as fully fledged subscribers, but just as an independent system connected through back-end servers that act as gateways between RFID and 5G.  
Apart from communication incompatibility, the main reason for this is that most RFID tags are not capable of implementing the cryptographic functions required for secure communication (ciphering and integrity check) and to compute the cryptographic results required to complete the 5G-AKA (authentication and key agreement) protocol, which the 3 GPP has established for the authentication of subscribers in 5G. As a way to overcome these problems, this paper proposes an RFID protocol which is totally compatible with 5G-AKA. In this 5G-compliant RFID protocol, each tag acts as a 5G subscriber, keeping its own credentials and carrying out its authentication, but the most hardware demanding operations, including the public key computations, are transferred to the reader. It is proven that this transfer does not endanger the security of the system, since the most sensible cryptographic material is not revealed to the reader at any moment. Thus, as 5G subscribers can operate with different devices (e.g., different smart phones), the tags can likewise be interrogated by different readers with the guarantee that previous readers cannot access current exchanged data.  
The outline of the rest of the paper is as follows. Section 2 describes the 5G-AKA protocol and the main 5G modules involved in the authentication procedure. Section 3 introduces the proposed protocol, detailing how the previous protocol can be adapted to be suitable for RFID systems. Then, Section 4 analyzes the security of this proposal and, finally, Section 5 concludes the paper.