## 1 Introduction  
With the advancement of power grids, the _smart grid_ concept was introduced to provide sustainable and affordable electricity in an efficient and stable manner. To explain the concept's schematic operation, smart meters record individual user's electricity consumption information and periodically report it to a control center, enabling adaptive and flexible transmission with minimal imbalances between generators and suppliers of energy. This next-generation power grid seamlessly integrates energy and information networks, in the direction of self-healing systems capable of controlling power generation and fluctuations in consumption. According to an IDC report [1], the worldwide smart grid market in 2017 is expected to be about $56 billion for electricity, gas and water technology. The term _smart grid_ has been defined by several national organizations such as NIST [2], IETF [3], and ETSI [4], as well as the research community [5; 6; 7; 8; 9; 10]. Although there are subtle differences in their definitions and characteristics, a smart grid has the following common advantages over traditional electric grid systems:  
* Energy awareness: By providing users with periodic energy usage patterns, pre-planned power consumption can be enabled. This can lead to consumer power-saving behavior through the implementation of energy-aware systems. In addition, \(CO_{2}\) emissions can be reduced, and the need for surplus power generation in backup plants can be avoided, which is beneficial to the environment and economics, through continuous electrical load balancing. * Increased power consumer selectivity: By allowing choices among various electricity generators, suppliers, and communication services, more options can be given to energy consumers. It imposes a more active role on consumers of new products, services and markets. * Improved reliability of power generation and consumption: Based on historical records of power usage, automatic power generation and consumption can be adjusted according to expected electricity demand. It also improves the resilience of the grid to natural disasters. Despite these benefits, increased attention has been paid to security and privacy issues threatening the successful deployment of smart grid systems [11]. Specifically, cyber security issues arise in information exchange, monitoring and controlling of electrical components. [PERSON] and [PERSON] [12] presented economic incentives obtainable by adversaries from electricity supply and demand, billing, and control information. For instance, measurement information can be used by adversaries for inference of users' behavioral patterns, implying privacy invasion [13]. Therefore, reliable aggregation of power usage information in a secure manner should be preceded because adaptive and adjustable power provisioning can be achieved only when metering information is aggregated reliably in advance. In this paper, we review the current status of the smart grid in terms of industrial and governmental activities for its distribution and popularization followed by state-of-the-art research trends focusing on aggregation and authentication of metering information. We then discuss our perspective on the smart grid market and future directions for the secure management of metering information, focusing on privacy-preserving data aggregation and authentication. Since the metering data integrity and its authentication are one of the most important security requirements in smart grid systems, this paper focuses on the authenticated aggregation in smart grid systems, which has not been profoundly surveyed in the previous works, such as [14] (covering only aggregation) and [15] (addressing a broad categorization about smart grid systems according to communication techniques, management objectives, etc.). Thus, contributions of this paper reside in investigating the current status of the development process and provisioning admirable future directions for reliable data aggregation in smart grid systems.