# From Bottom of Sea to Space: Quo Vadis IoT? So What About Security?
## 3 Security Challenges and Mechanisms
### IoT on the Ground
#### 3.2.1 Extensions with Applications in Medicine
The secret key agreement uses PUFs to allow devices to check the authenticity of a sensor node as well as a doctor's legitimacy before relaying information. The scheme has been robustly tested with the use of AVISPA tools and has performed well, preventing attacks such as MITM and using fewer systems than similar schemes. Also influenced by the pandemic, the authors of [86] propose a time-bound group key authentication using extended chaotic maps. These time-bound group keys allow for groups of devices to authenticate each other for a short period of time. This function is low-cost as the device does not need to retrieve a key every time it connects to the application layer, rather than encrypting and decrypting every time like other methods. The chaotic maps' unpredictable nature makes them useful in the authentication and key-agreement process of the scheme. For IoMT, it is important to protect the integrity and confidentiality of the data. The authors of [87], inspired by the pandemic, propose an Attribute-Based Encryption (ABE) method for providing user privacy and confidentiality. This method is a partially policy-hidden and large universe ABE model that is publicly traceable. An area of focus for the authors is that the amount of data is independent of the publicly available information; this allows for any amount of electronic health records (EHR) to be stored. In addition, any person who is in possession of the encryption key is able to easily track the data linked to it. The final area of focus of the system is that it will have fewer bilinear pairings, allowing for smaller costs during decryption. A big concern with most encryption is the cost of encryption and decryption. Using traditional encryption, there is a large cost of computation, making it an unfeasible way for patients' data to be transferred in real time. The authors of [88] propose a lightweight and efficient encryption algorithm that could be used efficiently in the transferring of image data. The method uses two permutation methods to secure the image. This new encryption method takes into account 256 bits to be encrypted and then breaks them into 16 different blocks of 16 bits. They have tested the algorithm on multiple test images and, when compared to the current standard, have proved to be much more efficient when considering execution time when compared to other similar forms of encryption. * Signcryption Encryption and electronic signatures are significant parts of the transfer of data securely. Signcryption is a system design that achieves privacy and authenticity without increasing the cost of computation by combining the digital signature and encryption algorithm. Other higher-cost models separate encryption from signing, creating a less cost-effective option. The authors of [89] propose the use of signcryption in conjunction with a publicly verifiable cloud-centric healthcare system. This system collects data from IoMT and outsources the data to the cloud server through the patient's smartphone. When tested by the authors, the scheme had less energy consumption compared to other related schemes. * Encryption The authors of [93] propose a symmetric key encryption to be used in IoHT. The method has a lower computational and communication cost than its asymmetric counterpart. The authors solve this issue through the use of a low memory symmetric key generation model that mimics group secret key agreements. The authors of [94] break down flaws in a current encryption technique based on chaotic maps, a conditional shift algorithm, and a modified Mandelbrot set [95]. When simulating an attack, the authors only needed one plaintext-ciphertext pair. Using this information, the authors performed a chosen-plaintext attack (CPA) and were able to crack the scheme with little computational time. To improve the system, the authors of [94] suggest using confusion and diffusion based on [PERSON]'s Theory [96]. Using the chaotic system, a substitution box can be created to satisfy the properties of confusion.