## 5 Conclusions and Future Work
One of the new algorithms covered here, the Authenticated Lightweight Encryption (ALE), uses a hybrid approach by mixing AES and a stream cipher called LEX. In a way, AES-CTR was also considered to resemble a stream cipher [44]. Thus, this leads us to continue our research to further investigate hybrid lightweight ciphers, which combine block and stream cipher properties. * **Leverage more robust devices at the edge to implement public-key encryption. ** Although many survey papers, such as [2; 18; 24], mention several schemes that use or adapt ECC as a key delivery and authentication method, [PERSON] et al. [86] proposed a new hardware architecture to implement the scalar multiplication to generate the session keys; it is still unclear if ECC keys can be generated and all the calculations performed at the smart devices. One study made it very clear how ECC-based lightweight cryptography [94] can be used in practical IoT systems. It included experiments in a testbed where ECC was used at the edge, in the gateways, such as Wi-Fi access points or a Sigfox base station. Such devices connect the IoT devices to the public internet. Located at the edge network, they support the smart device's mobility and can process the smart device's data (such as filtering sensor data). The proposed scheme uses ECDH as the public/private-key algorithm and to generate the session key for the AES symmetric encryption. Thus, a strong end-to-end encryption exists between the gateway and the application server. The authors explain that the smart device uses a \"low key\" to encrypt data to the gateway at the edge to provide a minimum level of security. This resembles the proposal by [PERSON] et al. [21], who advocated for applying security at the more powerful nodes that reside at the edge or fog network of the IoT system, which they call \"end-through-node-to-end encryption\". * **Customize or augment the application layer security of standard communication protocols. ** The only communication technology reviewed in this paper that provided end-to-end encryption was LoRaWAN. Even using LoRa, it is recommended to implement one's own application-level encryption to provide the required level of end-to-end confidentiality for one's application. The next application example explains this idea well, in which we use Zigbee but implement our own application layer security scheme in a hybrid FPGA/microcontroller module to protect the data. **Example Application. ** This review is part of a larger research project, which is developing different IoT prototypes. One of them is a vehicle-to-vehicle (V2V) communication system, which is an automated system of a lead-follow vehicle. One of its applications could be logistics. Based on our first lesson learned, we have communication in one direction only, with the lead car supporting only encryption and the follow car supporting only decryption. Based on our second lesson learned, this system's network environment is not a safe network and does not have any physical protections. In this V2V prototype system, the standard IoT communication technology is Zigbee. It has enough bandwidth to support the frequent updates sent from the lead car to follow the vehicle within a short distance. To control the following vehicle, the delay between updates should be less than 10 ms. Therefore, this application has strong confidentiality and real-time requirements. Processing delays due to security algorithms can impact the proposed operation of the system. As for security, the V2V system currently uses security level zero at the link layer. To compensate for this, a new application layer security protocol is being developed. The micro-controller used in this project is the Mixed Signal Processor 432 (MSP432) from Texas Instruments, which is an ARM-based micro-controller that supports AES encryption. To allow us to customize the application layer security, a hybrid ARM-FPGA module is being developed that will allow us to experiment with additional algorithms at the hardware level.