Аннотация: Nowadays, the number of Internet of Things (IoT) devices with a wide range of tasks is growing rapidly around the world. Many types of these devices collect data and, depending on their purpose, some data may be very sensitive to the user. This requires security on the device, which must protect the collected data and send it to the server via the Internet. This article describes some of the programming and debugging techniques developed using the Mbed platform running on the BLE Nano kit microcontroller. C ++ was used as the primary language instead of C to improve programming efficiency. This turned out to be a good choice, but it led to an increase in the size of the program. Thus, much of the optimization was spent on reducing the size of the program and data. The main purpose of this article is to describe the Advanced Encryption Standard (AES) symmetric encryption algorithm, its security and complexity, using the ARM Mbed special encryption library. In addition, the article demonstrated homomorphic encryption in C ++, it is a form of encryption that allows you to perform certain types of computations on encrypted text and generate an encrypted result that, when decoded, corresponds to the result of operations performed on simple texts.