The Internet of Things (IoT) is integrated and applied in various domains such as Smart Home, Healthcare, Industrial IoT (IIoT), and others. IoT allows physical objects to be able to create, receive and exchange huge amounts of data at any time. The goal of such applications is to automate physical objects that will be able to function without human intervention or with minimal intervention depending on the purpose of the application. Because all domains involved involve the use of sensitive data and that data is usually transmitted over insecure channels, security and privacy issues arise due to potential cyber-attacks. This paper presents various IoT security techniques as well as the main security goals and characteristics. Three types of authentication schemes, one-factor, two-factor, and threefactor are then explained. Since authentication is one of the most important security goals, a special focus is on two-factor authentication schemes.

The Internet of Things (IoT) connects almost all objects in the environment, whether they are physical or virtual using the Internet with the aim of creating new digital services that will improve lifestyle of the people. Currently, IoT devices cover a wide range of applications across the globe, such as smart cities, smart healthcare, smart transportation, smart homes, smart education, smart supply chains, smart agriculture, wearable devices, Industrial IoT (IIoT), smart energy where several have a direct impact on our daily life activities. With the advent of the Internet of Things, the size of the network has expanded beyond all boundaries, in which various IoT applications generate enormous amounts of data and require continuous Internet connection for communication between devices. Despite the countless benefits that IoT provides, there are some security challenges in this scenario. As data is communicated through wireless networks, challenges in the security domain can be such as data confidentiality, data authentication, data reliability, privacy.