With the advent of advanced technology, the IoT has made possible the connection of numerous devices that can collect vast volumes of data. Hence, the demands of IoT security is paramount. Cryptography is being used to secure the authentication, confidentiality, data integrity and access control of networks. However, due to the many constraints of IoT devices, traditional cryptographic protocols are no longer suited to all IoT environments, such as the smart city. As a result, researchers have been proposing various lightweight cryptographic algorithms and protocols to secure data on IoT networks. This paper discusses state-of-the-art lightweight cryptographic protocols for IoT networks and presents a comparative analysis of popular contemporary ciphers. In doing so, it has classified the most current algorithms into two parts: symmetric and asymmetric lightweight cryptography. Additionally, we evaluate several recently developed block cipher and stream cipher algorithms in terms of their security. In the final section of this paper, we address the changes that need to be made and suggest future research topics.