I am using an ESP-01 this way: MCU <-> UART <-> ESP-01, using AT firmware/NonOS on ESP-01.
I have my own encryption functions, and I would like to implement them both on MCU and ESP-01 sides at least for data packets, like those packets where ESP-01 send a data packet to the MCU starting with "+IPD" string, and also for the data that is sent from the MCU to the the ESP-01 after the MCU have sent the command AT+CIPSEND=n, being 'n' the quantity of data bytes to be sent.
Will I be able to to such modification on ESP-01 side? I mean, edit the NonOS "at"firmware? As I was looking, there is only few source files and much .a lib files in the folder of the SDK.
I want to do such encryption because my data is circulating unprotected between the ESP and the MCU. In my application, I use a SSL/TLS connection as internet client with the ESP with Google's Firebase database, but this way anyone could sniff my data by monitoring the UART signal. And to say, I am not able to use SSL/TLS (like mbedtls) inside the MCU because the MCU has limited flash memory size.
I already donwloaded the "ESP8266_NONOS_SDK-2.2.1", compiled it with virtual machine and did the download of the generated bins to the ESP-01, my question here is about the possibility to customize the "at" firmware.
Any suggestion for this case?