# IoT Technologies during and Beyond COVID-19: A Comprehensive Review
## 6 Challenges for IoT
### Research on Mitigation of IoT Privacy and Security Threats  
The authors in [80, 81] focused on developing a security architecture for the challenges and security issues that IoT technology faces. The generic layering system is as follows: the perception layer, which includes RFID and different sensors to identify objects; the network layer (Internet and mobile network) that is responsible for transmitting the data; the middle-ware layer that processes, stores, and links different information; and finally the application layer, where practical applications exist. Each layer contains different challenges, such as unauthorized access to tags and tag cloning in perception layer, DOS and sybil attack in the network layer, and sniffing and malicious code injection in the application layer. To face these challenges, hash and encryption mechanism was suggested in the perception layer, IDS in the network layer, and firewalls in the application and middle-ware layer. The security goals were confidentiality: to ensure that sensor nodes data is not revealed, integrity: to ensure data is not altered by any means, and availability: to ensure data is always available. A study conducted by [82] provides a block chain approach where it can be more secure and add more privacy gains. This approach also affects the processing time, traffic, and energy consumption, but all that is bearable, compared to the privacy advantages it brings. The process works by having a local block chain that keeps track of communication and data between devices. Each device asks for certain data to offer services. Additional delays are not significant and do not impact the availability of the smart home device. Using this method prevents DDoS attacks by checking all outgoing traffics and making sure the data is authorized by the device. It also prevents linked attacks by using a unique key for each communication between the devices. Another study [83] tried to overcome the challenge, where, when thousands of IoT devices are connected, a current model of server-client is used, which has some issues and limitations, and proposed a blockchain IoT system. Ethereum differentiates from a server-client model by being a distributed computing platform and data transactions are stored via consensus algorithm that attackers cannot figure or tamper with easily. This method prevents DoS and DDoS network attacks. One of its weakness is that Ethereum will not fit time-sensitive applications, as it needs time for transactions to happen. The second issue is storage that lightweight IoT devices will need, as it may require large storage. The author in [84] suggests more research on implementing techniques and algorithms to improve the efficiency of IoT security, especially the security of ender-users, and focuses more on metaheuristic algorithms that can achieve excellent solutions. The use of Non-Dominated Sorting Genetic Algorithm (NSGA-II) offers effective solutions to solve the problem of optimizing Wireless Mesh Network (WMN) infrastructure placement [85]. For a highly effective way of finding a set of effective solutions, metaheuristic algorithms may be considered for solving IoT security issues. A hybrid encryption algorithm was proposed by [86] for data confidentiality, integrity, and non-repudiation in IoT technology. IoT is a new network that seeks to achieve intelligent processing, reliable transmission, and perception of information by using RFID and wireless sensor connections. There are many security concerns related to wireless communication, network transmission, RFID, information processing, and privacy. The proposed algorithm uses a public key cryptography as it has less memory demand and high encryption speed. The method starts by generating a public key using symmetric encryption; the message is then encrypted by an asymmetric algorithm. The receptor that owns a private key decodes the message by private key and asymmetric algorithm. The algorithm combines both Advanced Encryption Standard (AES) and NTRU algorithms.