IoT is becoming more and more popular, along with the massive availability of cheap and easy-to-use IoT devices. One protocol that is often used in IoT devices is the MQTT protocol. By default, the MQTT protocol does not activate encrypted data security features. This MQTT default feature makes the transmitted and received message data vulnerable to attacks, such as eavesdropping. Therefore, this research will design and implement encrypted data security using the Lightweight cryptography algorithm. The focus of this research will be on securing MQTT message data at the application layer. 

Security at the Application layer needs to pay attention to the selection of cryptographic algorithms used considering that IoT devices have limited resources. Lightweight cryptography is recommended because its lightweight design matches the characteristics of IoT devices that have limited resources. Some of the Lightweight Cryptography algorithms have been published in several international journals, one of which is the Lightweight Encryption Algorithm (also known as LEA) algorithm which is South Korea's national Lightweight Cryptography algorithm based on block ciphers. The challenge in implementing the LEA algorithm in the MQTT protocol is the selection of MQTT variables to be encrypted. This selection must be careful so as not to disrupt the workflow and process of the MQTT protocol. This research will analyze the effectiveness of the LEA algorithm compared to other lightweight algorithms in performance time. This analysis will compare the results of this research with some previous research.