- What is it?
- Why is it needed?
- Project foundation
- How does it work?
- Security and encryption
- Technical limitations
- What do you need to get started?
- Wiring diagram
- Modifications and customization
- Key generation
- Power supply and enclosure
- Background
- Important!
- Feedback
ME-LO-RA NETWORK is a mesh network based on the ESP32 microcontroller and LoRa (SX1278) radio module, designed for transmitting text messages between users over radio using:
- RSA asymmetric encryption,
- SHA-256-based digital signatures,
- Message delivery confirmation.
This project enables secure and anonymous messaging when traditional communication channels are unavailable or disrupted (e.g., during mobile internet outages).
- Microcontroller: ESP32
- Radio module: LoRa SX1278
- Additional components: OLED display, button.
- The ESP32 creates a Wi-Fi access point and hosts a web interface for sending/receiving messages.
- All messages are encrypted using RSA and digitally signed; message integrity is verified via SHA-256.
- The recipient validates the signature and decrypts the message.
- A signed acknowledgment message is sent back to confirm delivery, preventing third parties from spoofing receipt.
- The network operates on a mesh principle: messages can be relayed through intermediate nodes.
- Any RSA key length is supported, but due to ESP32 performance constraints, 64–128 bits are recommended.
- An additional security measure is a limited and shuffled character set. This set can be modified, but must be synchronized among all chat participants (not required for relaying).
- Public keys and aliases are broadcast publicly (e.g., via the ME-LO-RA broadcast channel).
- No network participant knows the true identity of the sender—only the recipient’s alias is visible.
- For enhanced security, it is recommended to remove all debugging output (e.g.,
Serial.printandSerial.println).
⚠️ Warning: Without synchronized character sets and ordering, message decryption between users will fail. It is recommended to leave these settings unchanged.
| Environment | Range |
|---|---|
| Dense urban area | ~500 m |
| Forest | ~1,000 m |
| Line-of-sight | up to 5,000 m |
- Number of relays: unlimited.
- Assembled device based on ESP32 + LoRa SX1278.
- A unique alias (nickname). If aliases collide, messages from others will appear corrupted and unreadable.
- A generated RSA key pair (public and private).
- Exchange your public key and alias via a public channel (e.g., ME-LO-RA broadcast).
The more network participants know your public key and alias, the more effective mesh relaying becomes.
⚠️ Caution: The shown ESP32 power supply schematic is not recommended. Use at your own risk!
✅ Recommendation: Power the ESP32 via the 5V/VIN pin using a boost converter to 5 V. If unavailable, connect the battery directly to 5V/VIN. In this case, the controller will shut down at ~3.9 V battery voltage but will not be damaged.
| ESP32 | LoRa SX1278 |
|---|---|
| GND | GND |
| D5 | NSS |
| D2 | DIO0 |
| D18 | SCK |
| D19 | MISO |
| D23 | MOSI |
| D14 | RST |
⚠️ Never power the LoRa module from the ESP32’s built-in 3.3V regulator, as this may damage the controller.
| ESP32 | OLED |
|---|---|
| 3.3V | VCC |
| GND | GND |
| D22 | SCL |
| D21 | SDA |
| ESP32 | Button |
|---|---|
| D16 | Contact 1 |
| GND | Contact 2 |
- D35 – pin for measuring battery charge level, connected via a voltage divider as shown in the diagram. Higher-value resistors (e.g., 50 kΩ) may be used.
The project is easily adaptable to your needs:
- The web interface can be fully customized (styles, logic, etc.).
- Just ensure the POST request structure to the ESP32 remains unchanged.
A Python script is included in the repository to generate RSA keys using prime numbers up to 31 bits.
Finding large primes is computationally intensive, so simplified primality tests may be used.
- The enclosure is designed for through-hole mounting (a compact PCB version is planned) and uses a 18650 battery as the power source.
- A 3D model of the enclosure is included in the repository—you can 3D-print it.
- Screws used: M5 × 12 mm. To install them, insert or press nuts into the corresponding slots in the enclosure.
- Before installing the ESP32 into the enclosure, it’s recommended to add an internal duplicate "Boot" button for convenient firmware updates.
The idea emerged during widespread mobile internet outages in Russia.
ME-LO-RA is a response to the need for an independent, anonymous, and secure messaging system during digital “shutdowns.”
This project is developed by a single person and is provided “as is.” Use it entirely at your own risk.
- Email: [email protected]
- Telegram: @TO_21_21
🌐 ME-LO-RA NETWORK – communication freedom without intermediaries.