ESP8266 Smart Weather Clock License Keygen

How It Works

The Smart Weather Clock (aka Small TV) validates devices using a license key derived from the device's MAC address. The algorithm uses a progressive CRC-8 calculation with a predefined template to generate a unique 12-character hexadecimal license key.

Algorithm Details

Component	Value	Purpose
CRC Polynomial	0x07 (x⁸ + x² + x + 1)	Bit diffusion algorithm
Initial CRC	0xCD	Starting value for CRC calculation
Template Array	[0x19, 0x56, 0xAD, 0xC0, 0xB3, 0xF3]	Salt/initial state

Algorithm Steps

1. Initialize a 6-byte working array with template: [0x19, 0x56, 0xAD, 0xC0, 0xB3, 0xF3]

2. For each position i from 0 to 5:

   • Replace working_array[i] with MAC[i]
   • Calculate CRC-8 over the entire 6-byte working array
   • Store CRC result as license[i]

Step-by-Step Example

For MAC 40:91:51:64:39:CF:

Step	Working Array	CRC Result	License Byte
1	[40, 56, AD, C0, B3, F3]	0xB4	B4
2	[40, 91, AD, C0, B3, F3]	0xC2	C2
3	[40, 91, 51, C0, B3, F3]	0x29	29
4	[40, 91, 51, 64, B3, F3]	0xCA	CA
5	[40, 91, 51, 64, 39, F3]	0xFE	FE
6	[40, 91, 51, 64, 39, CF]	0x4A	4A

Final License: B4C229CAFE4A

CRC-8 Calculation

For each byte in the working array:

1. XOR with current CRC value
2. For 8 bits:
   • Shift left by 1
   • If MSB was set, XOR with polynomial 0x07

def crc8(data):
    crc = 0xCD  # Initial value
    for byte in data:
        crc ^= byte
        for _ in range(8):
            if crc & 0x80:  # Check MSB
                crc = ((crc << 1) ^ 0x07) & 0xFF
            else:
                crc = (crc << 1) & 0xFF
    return crc

Each license byte depends on all previous MAC bytes plus remaining template bytes

Usage

# Basic usage
python3 keygen.py 40:91:51:64:39:CF