# A Survey of Internet of Things (IoT) Authentication Schemes +
## 5 Analysis of IoT Authentication Schemes
### Smart Grids  
Smart grid is taking the momentum over traditional power grids due to its efficiency and effectiveness, but security issues are still challenging in such field. In [70], the authors proposed an authentication scheme based on a Merkle-hash tree. Each home is equipped with a smart meter to collect the consumption of electricity for a time interval and sends the data via wireless communication to the Neighborhood Gateway (NG). The NG sends these data to the control center to collect the bill, which is sent back to the customer. The main contribution is the mutual authentication done between the smart meter and NG using a lightweight scheme that has an efficient computation and communication overhead. The authors of [71] also provided an effective and robust approach to authenticate aggregated power usage data in Neighborhood Area Network (NAN) with a fault-tolerance architecture, which is based on digital signature. In [72], the authors proposed a protocol to authenticate Home Area Network (HAN) smart meters with the smart grid utility network, and provided a new approach for key management. While developing a smart grid, two main features should be taken into consideration: the data sent to the control unit or gateway should be sent from a valid smart meter, and there should not be a way of bring out the style of the customer by analyzing his consumption of electricity, thus breaking his privacy. In [73], the authors took the above features into consideration and developed an authentication scheme (called PASS) for smart grids based on Hash-based Message Authentication Code (HMAC). Such approach also ensures the privacy of the customer. To achieve a lightweight message authentication scheme for smart grid, the authors of [74] built an approach that allows smart meters to mutually authenticate to other system components and achieve message authentication. The authentication is done using a lightweight Diffie-Hellman and the data integrity is achieved using HMAC. In [75], the authors proposed an authentication protocol for smart grids called Smart Grid Mutual Authentication (SGMA) and another scheme called Smart Grid Key Management (SGKM) for key management. The scheme benefits from the traditional protocols and enhances them to achieve mutual authentication and key management. It uses the Secure Remote Password (SRP) [76] that depends on the password entered by the requester to generate a verification ID for further communications, but the enhanced version has less overhead with respect to the exchanged handshake messages and number of packets. Public Key Infrastructure (PKI) is used for key management but due to its overhead regarding the key regeneration, an enhanced version of ID-based Cryptography (EIBC) is used with PKI by replacing the public key with the identity of the requester. In [77], the authors proposed a lightweight authentication protocol for smart grids. It consists of three tiers by using three different protocols for different purposes: Diffie-Hellman is used as key agreement protocol, with the use of RSA and AES for achieving the confidentiality, and HMAC for maintaining message integrity. To address some performance and security challenges such as the storage cost and the key management, the authors of [78] discussed one-time signature to be used for multicast authentication in smart grids. The authors of [79] proposed a Privacy-preserving Recording and Gateway-assisted Authentication (PRGA) protocol for a hierarchical smart grid network with a gateway-based authentication. The scheme is based on HMAC and homomorphic encryption to authenticate and aggregate the messages sent by smart meters before sending them to the control center. This reduces the amount of exchanged data. The main advantage of such scheme is keeping the identity of the smart meter hidden to the gateway and the control center until the time of generating the bills, thus ensuring privacy.