# A Survey of Internet of Things (IoT) Authentication Schemes +
## 5 Analysis of IoT Authentication Schemes
### RFID and NFC-Based Applications  
Radio Frequency Identification (RFID) is a wireless technology that consists of tags that can be attached to any physical object or even humans; its main purpose is the identification or detection of the tagged objects. RFID can be deployed in various fields, e.g., supply chain, health care, climate sensing, etc.  
In [81], the authors suggested a lightweight authentication protocol for RFID tags based on PUF. The protocol consists of three transactions: tag recognition, verification, and update. In the first transaction, the tag reader recognizes the tag. The second transaction is the verification, where the reader and the tag mutually verify the authenticity of each other. In the last transaction (Update), one should keep up the most recent used key for the next verification.  
To protect the supply chain of connected devices, the authors of [82] enabled authentication and perceptibility of the IoT devices, through an RFID-based solution. The authentication process consists of two steps: checking the connectivity between the tag and the IoT device and then approving the perceptibility of the tag.  
In an IoT-RFID based system, the RFID reader is connected to the Internet to form an IoT end device. On the other side, it is connected to the tagged items via RFID communication protocols. The tagged item is portable and moves from a reader to another, thus there is a need for verifying the identity of each other via authentication. Due to the absence of cryptographic features in RFID, the system is vulnerable to security threats such as impersonation or cloning attacks. In [83], the authors presented an authentication protocol to be used in IoT-RFID use case with the use of lightweight encryption algorithm.  
To resist against cloning attacks to the RFID tag, the authors of [84] proposed an offline authentication for RFID-tags based on PUF. It combined both identification and digital signature security protocols. In the authentication, the tag generates a secret key by challenging the PUF and collecting the response. Such response with the helper data will create a certificate that will be stored inside the ROM of the tag. Next, the verifier authenticates the tag by checking the validity of the certificate. To provide anonymous authentication for RFID systems, the authors of [85] presented a PUF-based authentication scheme for classic RFID tags. Then, they provided an enhanced scheme for noisy PUF environment. The main drawback of such scheme is not taking into consideration re-feeding the server with new Challenge-Response Pair (CRP) when the existing pool becomes empty.  
The authors of [86] proposed a two-factor authentication scheme based on smartphone with Near Field Communication (NFC) feature as first factor and fingerprint of the user as the second factor. Both factors are used to authenticate user on smart library system. The library database then checks if the personal data embedded in the NFC tag and the fingerprint match then the user is authorized to access the internal library network to query for books and providing the user with the rack position (location) in which the book is located.  
The authors of [87] proposed a mutual authentication scheme for IoT RFID-based applications in fifth-generation mobile networks (5G) by providing the reader with a cache, to store the keys (used for authentication) for the recently visited tags, to speed up the authentication, reduce the computation cost and increase the security in storage.  
The authors of [88] proposed a mutual authentication scheme for IoT NFC-based applications in 5G. By using only (lightweight) Shift and XOR operations to suit the performance and storage features of NFC tags, they provided the anonymity of the tags using pseudonym instead of the real identity.