/ESP8266-OTP-Generator

Generates OTP codes based on NTP time and shows them on an I2C display.

Primary LanguageC++MIT LicenseMIT

ESP8266 OTP Display

Overview

This repository contains an Arduino sketch for an ESP8266 module equipped with an I2C display. The sketch is designed to connect to a specified Wi-Fi network, synchronize the time with an NTP server, calculate a One-Time Password (OTP) based on a secret key, and display this OTP on the screen. This functionality is typically used in two-factor authentication systems.

Prototype using a Wemos D1

A suitable case can be found here: Wemos D1 Case with Display on Thingiverse

OTP Generator in 3D-Printed Case

Features

  • Connects to a predefined Wi-Fi network.
  • Synchronizes time with a specified NTP server.
  • Calculates and displays two Time-based One-Time Passwords (TOTP) on the I2C display.

How to Use

  1. Set up your ESP8266 environment: Ensure that your Arduino IDE is configured to program the ESP8266 and that all necessary libraries (ESP8266WiFi, WiFiUdp, NTPClient, Wire, SSD1306Wire, TOTP) are installed.

  2. Configuring the sketch:

    • Update the Wi-Fi credentials (ssid and password) in the sketch with your network's details.
    • Set the NTP server address and the UTC offset in seconds for your time zone.
    • Replace the placeholder for the secret1 and secret2 byte arrays with your actual OTP secret keys.
    • Replace the labels "OTP1" and "OTP2" if needed.

  3. Uploading the sketch:

    • Connect your ESP8266 to your computer and select the correct board and port in the Arduino IDE.
    • Upload the sketch to the ESP8266.

Converting Your Base32 Key

If your OTP secret key is in Base32 format (common with many authentication systems), you'll need to convert it to a byte array format to use in this sketch. You can use the following Python script to do this:

import base64

def base32_to_byte_array(base32_string):
    # Decode the Base32 string into bytes
    decoded_bytes = base64.b32decode(base32_string, casefold=True)
    return [byte for byte in decoded_bytes]

# Example usage
base32_secret = "YOUR_BASE32_SECRET"  # Replace with your actual Base32 secret
byte_array = base32_to_byte_array(base32_secret)

# Print the byte array in hexadecimal format
print("Decoded bytes in hex format:", ', '.join('0x{:02x}'.format(byte) for byte in byte_array))