# A Secure and Efficient Group Key Management Scheme for Clusters of String Inverters
## 2 Related Works
[26] propose a multicast communication scheme based on a publisher-subscribers architecture. The publisher is a Smart Grid's Human Machine Interface/Supervisory Control And Data Acquisition (HMI/SCADA) server (e.g., a phasor gateway) whereas the subscribers are customer's intelligent electronic devices (e.g., circuit breakers, transformers and capacitor banks). The scheme ensures mutual authentication between publisher and subscribers and secure delivery of multicast information. [PERSON] et al. [29] propose a tree-based key management scheme for secure unicast, multicast and broadcast communication in a Smart Grid network with millions of entities (e.g., Smart Grid facilities, smart meters and sensors). The protocol is based and extends a key management protocol for secure broadcast communications in pay-TV broadcasting systems [31]. The scheme is secure against three types of threats: (a) loss of confidentiality; (b) loss of integrity and (c) loss of availability. [PERSON] et al. [32] present a key management scheme for secure unicast, multicast and broadcast communication among various components in the Smart Grid, namely power grid control systems and remote sensors and meters. The proposed scheme employs the Iolus framework [45] for structured key management. The scheme supports the hierarchical structure of the Smart Grid's control mechanism, i.e., from top to the bottom: control centers, regional coordinators and remote end customers' devices. For this reason, the scheme provides two different key management mechanisms for upper and lower level communications. This is according to the different resource limits at two different levels. [PERSON] et al. [33] focus on the security of the Advanced Metering Infrastructure (AMI) because of its critical role for the security of the Smart Grid. AMI is responsible for two main tasks. On the one hand, to collect time-based data from consumer's smart meters and transmit them to AMI host systems. On the other hand, it is also responsible for implementing control commands from AMI host systems to customer's smart meters, so as to perform required control actions (e.g., mechanism that enable customers to cut down energy usage at peak times). In their paper, the authors propose a Multi-group Key management for AMI (MK-AMI) that support unicast, multicast and broadcast communications. The scheme guarantees: (i) confidentiality of customer's sensitive data; (ii) integrity of data (e.g., information and control commands) transmitted from customer's smart meters to AMI host systems and vice versa; (iii) data availability and (iv) non-repudiation. From the performance evaluation viewpoint, the authors show that MK-AMI achieves low storage and communication overheads. Summarizing, existing related works for secure group communication in the Smart Grid only focus on the intercommunication between Smart Grid's Operations and Customer domains. In this work, instead, we rather focused on the intracommunication among specific devices of the Customer domain, namely clusters of smart string inverters. To the best of authors' knowledge, we are the first facing the topic of secure group communication within the context of PV installations.