# SASC: Secure and Authentication-Based Sensor Cloud Architecture for Intelligent Internet of Things
## 1 Introduction  
In the last few years, wireless sensor networks (WSNs) gained a lot of research interest from the research community due to its dynamic nature and wide range of applications [1, 2]. A WSN comprises tiny smart devices called micro-sensors with limited memory, storage, processing, and battery resources. There are different kinds of sensors used based on applications such as measuring pressure, temperature, humidity, and mobility [3, 4]. All sensed information is further forwarded to the base station (BS) via the appropriate forwarding node called the cluster head. As the network size and nodes' density increases, the network scalability with data security is most of the challenging tasks for WSNs [5, 6, 7, 8, 9]. In recent years, many solutions have been presented to improve the routing and energy efficiency for limited constraints networks, however, most of them overlooked data authentication and security in the presence of malicious nodes. The dynamic nature of Internet of Things (IoT) systems allow an enormous number of heterogeneous physical and virtual objects and are interconnected via the Internet [10; 11; 12; 13; 14; 15]. The paradigm of IoT enables these objects to communicate with each other in a distributed manner, however, the communication provides a lack of trust in data security [16]. Moreover, IoT networks typically need to be optimized for energy consumption and load-balancing schemes and have to be developed to route the IoT system for a longer life with reliable data delivery. Therefore, developing an efficient and intelligent IoT communication system to ensure data security with network consistency is a demanding challenge [17; 18; 19; 20; 21; 22]. To transmit data packets towards the BS, the presented solution is categorized into chain based, tree-based, and cluster-based routing protocols. Chain and tree-based routing protocols forward data packets to the root node using the next-hop selection method usually based on distance factor. However, such methods have a high latency ratio and therefore they are not appropriate for large scale networks [23; 24; 25]. On the other hand, cluster-based protocols are mainly used in high-density scenarios and improve network performance in terms of lifetime and throughput [26; 27; 28]. In formulated clusters, ordinary nodes sense the targeting environment and forward information to associated cluster heads. Afterward, the cluster heads forward the gathered data towards the BS via a single or multi-hop transmission model. Additionally, the sensor-cloud has become a popular infrastructure due to the limited constraints on the sensor nodes, massive data processing, and data storage. However, cluster heads are operated independently and are therefore exposed to innumerable security threats in the presence of malicious nodes. Although different security routing solutions have been proposed by researchers for IoT based WSNs [18; 29; 30], they require some high computational mathematical and validation functions, which result in degrading network performance in terms of communication and processing overheads. Furthermore, most of the proposed solutions overlooked node authentication in the presence of malicious threats and may lead to compromised data security [31; 32]. Therefore, a secure sensor-cloud based architecture with node-level authentication is needed for real-time applications, aiming toward efficient data processing and data protection against malicious nodes. This article presents a secure sensor-cloud architecture for IoT based WSN to provide data security and easy to scale with efficient network performance. The proposed architecture's scope is the deployment of IoT-based WSN in the environment of smart cities. Numerous IoT sensors, identified with unique tags, are distributed in a smart city scenario to sense, gather, and forward data via intermediate gateways or cluster heads towards the BS. The BS is further connected with the cloud server using wireless communication technologies, such as WIFI, 4G, 5G, etc.