**1. Introduction**

Software-Defined Networking (SDN) is an intelligent architecture in networking. It decouples the control and data plane which helps to improve the network performance and make it scalable, secure, and programmable. Internet of Things (IoT) network embedded with sensors nodes, RFID tags, smart cards, low resource devices which can communicate and share huge data to provide services to the clients. It is too difficult to provide security to the IoT system in heterogeneous and large networks. To combine SDN and IoT in a single architecture as SDN-IoT, it can make the infrastructure plane controllable, smart, reliable, and scalable [1]. IoT has many applications in different areas such as smart cities, smart vehicular networks, and security surveillance. To make these secure, SDN plays a huge part since it controls

the whole network from its control plane. IoT devices capture and store sensitive information which is a great concern to make the network and physical devices secure from the eavesdroppers. 5G is the latest communication technology that is famous for low latency, massive connectivity, high throughput, and heterogeneous nature. By making SDN-IoT architecture in 5G, it can be flexible, dynamic and helps to improve the bad scalability due to hardware differences in heterogeneous environments. To make these happen there are many security challenges that need to be taken care of. One of the major necessities of 5G is low latency which is a real challenge with a huge growing market. Many cryptographic algorithms exist, but due to their high time and space complexity requirements, it will be a good choice to avoid these in a fast communication system like 5G. Recently, a lightweight cryptographic algorithm (LWCA) is a new area of cryptography applied in 5G [2]. These algorithms do not require much space, and the time complexity is also low which makes this technique applicable in IoT networks where limited battery life and strict physical constraints both need to be considered. Currently, many researchers tend to shift their focus from cryptographic aspects of security to lightweight security algorithms [3]. This helps the system to become less complex, provide high performance and also lower the cost. Traditional cryptographic techniques have high complexity as well as it is difficult to implement. In this chapter, we discuss different lightweight cryptographic algorithms and their applications in the SDN-5G network. There are three vulnerable areas in SDN-IoT architecture: Control Plane, Data Plane, and the Interfaces between Control and Data Plane due to their programmable nature and open access architecture.

LCAs are divided into four types: 1. Block cipher, 2. Stream cipher, 3. Hash functions, 4. Elliptic curve cryptography. Each of the techniques has its own strength and weaknesses. Based on the application's requirements, it can be used in different layers of SDN-IoT architecture. Block ciphers are AES, DES, DESL, DESX, DESLX, Piccolo, TEA, XTEA, mCRYPTON, PRESENT, TWINE, LBlock whereas SNOW-V and Espresso are the stream cipher presented in this chapter maintaining the strict requirements of LWCA. Apart from the above-mentioned algorithms also, GRAIN works as a stream cipher and can use as one of the LWC algorithms in the SDN-IoT network. It uses very few gates with high security and less power consumption. When it comes to security perspectives, HIGHT, ICEBERG, CLEFIA are good choices. Hummingbird holds both of the properties of block and stream cipher and can implement in both hardware as well software. This flexibility of implementation and maintaining the lightweight properties can use this technique in both the infrastructure and control layers of the SDN-IoT network in 5G. SHA-1, SHA-2, SHA-3, BLAKE2 are the algorithms used as Hash function techniques. We will discuss each of them and their applications in the SDN-IoT network later in this chapter. There are some application areas of cryptography where we work with such devices that operate on battery power and need cryptographic algorithms which consume less power, such devices are medical implant devices or environment-measuring devices. Although very few works have been done in this direction and many exposures are open for future research work in this subarea of cryptography which we mention here as lightweight cryptography (LWC). Most of the LWC algorithms can resist linear and differential attacks which are the basic criteria of any general cryptographic algorithm. It is important to measure the performance of LWC algorithms before using them in any application. One of the key criteria of the LWC algorithm is low latency. For that, some of the automobile sectors which require immediate response use LWC techniques for security purposes. IoT devices that require less CPU cost and memory

consumption such as smart TV, tablet PCs are the application area of LWCAs. Also, medical sensors, smart agriculture sensors, RFID tag applications, electrical home appliances, automobile industry are the different applications of LWCAs.
