Nowadays, the increasing number of devices deployed in IoT systems implementation and the requirement of preserving the integrity of data transported over the Internet, demand the use of data encryption schemes. This paper aims to show the performance evaluation of CP-ABE (Ciphertext-Policy Attribute Based Encryption) type of encryption over MQTT (Message Queue Transport Telemetry) that focuses on execution time for an IoT system with Raspberry Pi. For the implementation, two Raspberry Pi 4 Computer Model B are used for both the publisher and the subscriber, and a computer with Ubuntu 20.04 LTS operating system is used for the Broker and the Key Authority. The result of the present work provides relevant information on the execution times required in the CP-ABE encryption scheme to provide data integrity and fine-grained access control policy in an IoT system. The work demonstrates that the CP-ABE encryption scheme is suitable for IoT systems.