## 6 IoT Security  
Security is one of the major concerns for IoT because attackers or hackers can silently access data from sensors [92; 93]. Therefore, it is crucial to know the various recent security approaches for IoT. One such approach known as IDP (IoT-dependent data placement) isused for privacy preservation. In this suggested approach, the main objective is to optimize the access of data concerning time and resource utilization and minimize power absorption according to the limitations of data safety [94]. Power minimization and privacy preservation can be achieved using NSGA-ii (non-dominated sorting genetic algo.) algorithms. This approach was locally evaluated considering real-time health-related data from patient health profiles, and the approval task was performed by a cloud service [95]. One method based on an encryption approach known as radio-frequency recognition is also used to provide security for medical data [96]. The flow of data in a network environment is quite complex for health information, and data security relies on biometric security with resource limitations in wearable health tracking systems. Therefore, IoT is integrated in medical devices in which information is processed to optimize security for various medical applications. The service provided by the cloud consists of three servers, i.e., a database server, key-assigning center and authentication server. For healthcare data, secure cryptography is used based on a lattice framework. This system consists of four stages, i.e., data encryption, data decryption, key generation and a setup stage; a lattice polynomial is used as input for the first two stages, and key assignment is implemented in form of the public and private keys. The second stage is shared by the data server, and in the final stage, the data are treated as an input parameter and integrated with a random polynomial. If a user wants to forward a request to deal with medical data, the key-assigning center sends the hidden key pair to the data server through a secure channel, and the data server executes the blank text, taking the input and hidden key pair. Security has been deployed in low-energy Bluetooth in a variety of ways, the most secure of which is LE secure relation, which follows a numeric comparison approach, and the ECHO (elliptical curve Hellman--Diffie) algorithm, which involves the use of a private and public key for every device to achieve secure key sharing. Two keys in the form of a master and slave are used, i.e., a recognition-resolving key and a signature-resolving key [97]. Potential attackers can be prevented from using 128-bit advanced encryption standard. The attacker's identity, eavesdropping and man-in-the-middle can be effectively tackled using the security feature of low-energy Bluetooth. For Zigbee, various security features are available, some of which are optional and are used by network developers. The security modes of Zigbee are based on 128 advanced encryption standards with security keys, i.e., master, link and network keys. The optional master key is used to secure the sharing and creation of the link, whereas the network key is essential and is shared by all devices using a network layer security process that manages all transmissions inside the network. The link layer is used to secure transmission in the application layer [98]. In a recent study, it was found that by sniffing the link key, a network can be easily exploited during device joining. From a healthcare point of view, if Zigbee is to be deployed, it must follow all optional security processes and trustable key management protocols. In Sigfox, security is deployed using a private key attached to each message to minimize the chances of intercepting and spoofing attacks. Advanced attackers target the service provider and hardware node and may disclose the unique key, affecting healthcare systems.