ESP32 Command Control

A simple handler-agent like network with encryption, uses the ESP-NOW protocol.

Objectives

• Implement ESP-NOW device-to-device communication
• Analyze protocol security and encryption
• Build a simple network

Retrospect: Project is complete

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Architecture

    Handler
        |
        | ESP-NOW broadcasts
        |
    +---+---+
    |       |
Agent #1  Agent #2

The handler listens for special messages containing a shared secret (base64 encoded string) with certain message types. Example: An agent sends a type 0 msg, the handler receives & validates it. It adds the agent to a local list, waits for type 2 messages (heartbeats). The handler registers an agent as an encrypted peer when its first heartbeat arrives, so that heartbeat is unencrypted and all later ones are encrypted.

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Requirements

• 3x ESP32 DevKit boards
• USB cables
• Development environment: ESP-IDF

Project Structure

root/
├── handler/
│   └── main/
│       └── main.c
├── agent/
│   └── main/
│       └── main.c
└── README.md

Building & flashing

Note: Hold BOOT button before flashing (At least, I have to do this, on windows...)

Prerequisites

Install CP210x/CH340 USB drivers:

• Silicon Labs CP210x Drivers

MacOS (arm64 in my case)

brew install cmake ninja dfu-util

# setup ESP-IDF
mkdir -p ~/esp
cd ~/esp
git clone --recursive https://github.com/espressif/esp-idf.git
cd esp-idf
./install.sh esp32

# build and flash - X = handler or agent dir
cd X 
# activate esp dev env (i use an alias)
idf.py build
idf.py -p /dev/cu.usbserial-* flash monitor

Windows

Manually install the IDF tools

# open "ESP-IDF PowerShell"

# build and flash - X = handler or agent dir
cd X 
idf.py build
idf.py -p COM3 flash monitor

Usage

Flash Handler to one ESP32, Agent firmware to the others. Monitor serial output to observe communication.