# Energy-Aware Security Adaptation for Low-Power IoT Applications
## 2 Related Work  
As previously discussed, LoRaWAN is one particularly important LPWA communications technology and lays the ground for the implementation and evaluation of the architecture and controller proposed in this article. In regards to the management of security and energy, we note that LoRaWAN lacks the mechanisms to support its dynamic management and adaptation, given that three classes of end devices may be employed with fixed configurations in terms of energy [5]. In addition, the standard does not consider the possibility of adapting the level of security dynamically, and as such, the impact of security mechanisms on energy is predictable and unavoidable, irrespective of the devices' classes employed. We thus may observe the lack of dynamic adaptation strategies for security and energy, particularly strategies that may promote energy saving in the presence of attacks, even when employing class B devices, and that can also support extra protection by enabling security for end-to-end communications in the presence of relevant threats. Given the previous limitations, we are able to identify a number of research proposals over the years, with the goal of improving the security of LoRaWAN-based applications, as we proceed to discuss. The architecture in [6] considers the usage of a Public-Key Infrastructure (PKI), employed to issue a certificate for all network entities supporting secure communications. Communications are secure in terms of integrity and confidentiality, while a set of other security-related mechanisms are proposed to secure communications in the network, such as VPN, firewalls and SSH. In [7], the authors consider the addition of a third element to the LoRaWAN architecture, which is independently managed and used to create and distribute keys among the participating devices. In this proposal, end devices receive only their own session key, and the NS is unaware of the various session keys, which are managed at the application level. In addition, this work proposes to change the AppKey in each session, in order to prepare for difficult attacks. Each device stores the last timestamp received and compares it against the timestamp value of the next message, in order to prevent against replay attacks. Authors in [8] consider Blockchain to improve trust in the network server, as well as to contribute to improving the overall security of the network. Blockchain must be supported by the NS, frequently the only device with the required resources for this purpose, in contrast with end devices and gateways. In this proposal, a management component is added to the NS, which adds a hash of each transmitted message to the Blockchain. In [9], the authors propose to use Ephemeral Diffie-Hellman Over COSE (EDHOC) to renew the keys employed for encryption of communications between sensing devices. EDHOC is a symmetric key management protocol employed between end devices and is based on SIGMA-I and implements the Elliptic Curve Diffie-Hellman algorithm (ECDH) with P-256. This new mechanism is used to renew session keys as soon as the device is activated, adding flexibility to the entire key management process. Another approach considered in [10] proposes that key management can be performed through public keys without the use of certificates, thus implementing Certificateless Public-Key Cryptography (CL-PKC). This is a lightweight method in terms of the memory and computational resources required and is therefore considered a good choice for IoT networks, given the typical constraints of the devices employed. In [11], the authors address the formal evaluation of LoRaWAN security against known threats. The authors employ the Scyther tool to investigate and expose weaknesses in LoRaWAN security. Besides the enumeration of vulnerabilities, the authors also discuss possible approaches to each of the identified vulnerabilities. In [12], the authors focus on jamming attacks against LoRaWAN environments. To mitigate this threat, the authors propose a LoRaWAN-based IDS module deployed on gateways.