## 1 Introduction  
The smart grid (SG) refers to a revolutionary power delivery system with several notable features like balancing supply-demand, monitoring inflicted loads, and integrating distributed and renewable energy that provides electric power to the consumers in a more efficient, reliable, and stable manner [1]. It is expected that in the future smart grid, the demand response (DR) technology will enable consumers to efficiently use and pay for the required electricity by reducing or shifting the usage during peak hours in order to maintain the demand-supply balance in the electric grid [2]. Similarly, monitoring dynamic loads and the integration of distributed and renewable energy enable the maximum utilization of sharing energy resources and efficient management of the power requirement in the system. In the traditional power grid, the electricity is delivered to the consumers with one-way flow. On the other hand, the SG provides a two-way electricity and information flow between the supplier and the consumers of electric power. To enable these features, information exchange between different components of the smart grid is necessary. Generally, a neighboring gateway (NAN-GW) collects electricity consumption information from smart meters (SMs) and sends it to the CC of the nearest substation through remote terminal units (RTUs) via wireless networks or wired link [3]. An overview of the smart grid network architecture is illustrated in Figure 1.  
Security and privacy issues are one of the most important challenges faced by the future smart grid. These issues include lack of mutual authentication between communicated entities, risk of various cyber-attacks, unauthorized access to the resources, revealing of device's and network's private information to the communicating entity, _etc._ The requirements of the SG network are different from that of the traditional information network. Most of the information network deals with confidential information. Hence, they prioritize the confidentiality first then the integrity, and least the availability of information. On the other hand, the SG network is primarily responsible for the availability of information, as well as the integrity protection of the message, and then the data confidentiality and privacy [4]. Before allowing any entity to have an access over a network and its associated resources, it is required to authenticate the entity, which may be a device or a user, and then verify the authorization and control policy based on the entity's identity. Authentication verifies the user's identity while the authorization verifies whether the user has valid permissions to access the requested resource. Authentication is one of the key challenges in the SG communication. The modern power grid makes use of supervisory control and data acquisition (SCADA) systems with communication protocols. Unfortunately, protocols used in these systems are often vulnerable to man-in-the-middle (MITM) attacks, replay attacks, impersonation attacks, and the cryptographic keys used in various devices of the system might be compromised [5]. Connecting the SCADA system with other communication networks (e.g., Internet) significantly increases security and privacy threats [6], and is one of the major challenges in many countries around the globe [7]. Many researchers are actively working to build secure and efficient authentication protocols in order to solve various communication challenges, and security and privacyissues exist in the SCADA [8; 9], home SG environment [10], security management and the SG operation [11], message delivery in the SG [12], and vehicle-to-grid (V2G) systems [13]. Secure integration in the SG network is also strongly required as various modules and entities receive data input from different other modules and send data output to several modules and entities. In such scenarios, maintaining data integrity and the secure integrated communication among various entities and control modules are necessary.