## 2 Authentication in the Smart Grid (SG) Network
### Authentication Protocols
#### 2.2.6 Obj-7: Confidentiality and Privacy  
Data confidentiality is required when we need to send some information in unreadable format over the network. For example, the AMI is accountable of collecting and transferring data and commands among the central controllers, AGs, and SMs. All the SMs send their data to the AG in the encrypted form so that the untrusted AG can no longer know the exact metering data values received from each SM. In authentication schemes, the sender needs to send a secret key or some number value to the recipient in a secure manner. The AMI is also prone to many privacy concerns. The privacy of the customer in terms of power usage, billing, and other information must be preserved during the authentication along with the privacy issues related to the SMs, such as data collection, transmission and other information. We also need to protect (hide) the actual identity of each device, such as SM, over the SG network so that the adversary cannot keep a track. Many times, it requires that the AG or CC should not know some specific information of the home users. In such situation we should implement both, privacy (to hide the actual SM/user identity over the network) as well as confidentiality (to send secret key or other parameter to the recipient over the SG network). An authentication scheme must overcome these privacy concerns and generate as little overhead as possible among AMI entities. In fact, we need to provide authentication, integrity, and confidentiality services together for a secure authentication scheme. In this direction, [PERSON] _et al._[68] proposed an identity-based authentication protocol, which offers source authentication, data integrity, and non-repudiation services. This scheme also preserves customers' privacy in AMI. However, it does not justify other expected protocol capabilities, including overhead, cost, and efficiency. [PERSON] _et al._[69] presented an integrated authentication and confidentiality (IAC) protocol, which provides mutual authentication between the SM and the AMI network, and enables data privacy, integrity, confidentiality, and trust services. The IAC scheme performs better in terms of packet loss and end-to-end delay. Although, it also proposes a hop-by-hop data aggregation using a network routing backbone [70], which is a deciding factor for information route optimization [71], it does not provide a full authentication in the HAN-AMI environment. [PERSON] [72] proposed an open metering system (OMS) security protocol for secure SM communication, which employ a mutually-authenticated SSL protocol also in the local metrological network using an additional authentication and fragmentation layer (AFL).  
In order to prevent from revealing the electricity usage patterns, a privacy-preserving scheme using a tamper-resistant device and pseudo identities is adopted by [PERSON] _et al._, in [73]. However, the attack analysis and overheads computations are not performed. Recently, a privacy-preserved scheme is proposed by [PERSON] _et al._, that does not allow the CC (power operator) to know which user has made the request using more/less power until the power is actually used [74]. [PERSON] _et al._[75] proposed an efficient privacy-preserving authentication for lossless data aggregation scheme (PALDA) that provides privacy preservation when collecting total sum of energy usage for a group of smart meters and when collecting individual energy usage of individual smart meters for a desired period of time. However, security analysis of the scheme is not discussed in detail.  
Based on these objectives, we evaluate existing protocols in terms of security and efficiency. Table 3 summarizes the existing authentication protocols.