# Dynamic Group Management Scheme for Sustainable and Secure Information Sensing in IoT
## 1 Introduction  
The Internet of Things (IoT) tries to connect with all objects based on the communication network and provide people with the intellectual technologies and services that communicate between person and object, or object and object. For this purpose, IoT devices process various kinds of information at different service fields. At this time, the IoT environment is analyzed from various perspectives such as environment, economy, and infrastructure, among others, and the device is deployed depending on the analysis results. The deployed devices can sense and process simple ambient information such as temperature or humidity, or they can process personal information such as the position of an individual. In the case of handling simple ambient information, priority may be placed on service sustainability rather than security for energy efficiency. However, even when only simple ambientinformation is processed, it is hard for services such as smart energy or smart vehicles to place priority solely on energy efficiency, as they are closely related to the public and individual's security. Therefore, IoT devices shall provide people with a service environment in which both sustainability and security shall be achieved. Especially, the sensor that collects information at the front line shall be ensured of sustainability and security. This is because sustainability and security at the sensor ultimately leads to the service provided to the users. The characteristics of IoT service are as follows. The IoT environment provides users context rich services based on user experience. At this time, user experience is based on the information collected from various objects that are available around users. Moreover, the most fundamental object among these diverse objects providing information is a sensor [1,2]. The quality of service to be provided to users through IoT shall be determined based on the quality of information to be collected and analyzed. That is to say, the quality of service to be provided through IoT shall be determined when it is possible to collect information from an authenticated sensor securely through a sensor network [3,4]. A sensor network infrastructure consists of the sensor nodes that synchronize or transmit the information detected through sensing to a server via other wireless network devices. Because of the characteristics of wireless communication, sensor nodes have been vulnerable to attacks such as relay attack, replay attack, and eavesdropping. The vulnerable authentication and management of the key may lead to infection by malicious codes such as Stuxnet, or an attack by malicious firmware updates, which in turn could develop into IoT device-based distributed denial-of-service (DDoS) by the second attack. Eavesdropping may expose the privacy of an individual who uses the IoT device to others, and an attack of retransmission may cause damages such as unfair penalty. Thus, security protocols and schemes have been adapted. Even the sensor node supporting the encryption such as RC5 and public key was developed [5, 6, 7]. However, those sensor nodes whose hardware computing power and energy resources are very limited compared to the other sensor nodes are not suitable for the use of encryption and secure communication requiring a high degree of computing power, which are used in the existing schemes and protocols. In addition, the studies to prevent relay attack have tried to detect transmission device location on wireless network topology using radio frequency signal analysis. On that account, it is not appropriate to utilize it in a sensor with mobility or a sensor whose energy is relatively limited compared to the other sensors [8, 9, 10]. The quality of intelligent services in the IoT environment can be enhanced when the information is collected mainly from users on a continuous basis. That is to say, it is imperative to collect and transmit data continuously from a sensor [1,2].