In the world of education, technology has been widely employed to increase the quality of learning activities in order to attain the intended results. Students must be prepared with necessary competences in order to succeed in a highly competitive global environment. One form of technology that is used as a learning medium is Android-based media which has benefits and can facilitate many aspects of learning. Learning computer security with the topic of cryptography involves complex mathematical calculations. This makes it harder for students to grasp the lesson. For this reason, an Android-based Computer Security System learning media was created to help students understand and study learning. This research resulted in the application of learning media for Computer Security Systems using the RAD method in its development. Application testing uses a blackbox test and shows that the application runs well on the Android operating system.