**Abstract**

Lightweight cryptography (LWC) is an area of cryptographic techniques with low computational complexity and resource requirements. There must be a reason for using it in Internet of Things (IoT) network with a strict resource constraints environment. The key features of a 5G network are low latency, high throughput, heterogeneous network architecture, and massive connectivity. A new area of network architecture called SDN-IoT comes into the picture to control and manage IoT devices in a network with low latency and high throughput. SDN helps to reprogram the network according to the application's requirements. Also, higher mobile applications lead to higher data growth. SDN helps to secure, manage, and control the huge data in the network. SDN-IoT architecture divides the network into three layers: The infrastructure layer, the control layer, and the service or application layer. In this chapter, we are focusing on the LWC algorithms from different perspectives so that they will fit into different layers of SDN-IoT network. We will discuss all the pros and cons of implementing LWC algorithms in hardware and software environments and also, the different layers of the SDN-IoT network. We also discuss SDN security architecture and different performance metrics for LWC algorithms.

**Keywords:** lightweight cryptography, SDN, IoT, 5G, SDN-IoT security, architecture, cryptographic algorithm
