How to parse encrypted binary data of vehicle positioning terminals and extract positioning information?

This document describes how to parse encrypted binary data from a vehicle positioning terminal and extract location information. Let's improve the clarity and structure.

Problem Description

I have a vehicle positioning terminal (a GPS device) that has been activated and configured with an IP address and terminal number. The server receives data from this GPS device in binary format, as shown below:

<code>b'~\x01\x00\x00!\x01ea8f\x97\x00\x00\x00,\x01/70111kg-12a\x00\x000000000\x01\xd4\xc1b88888\xe5~'</code>

However, no matter what decoding method I use, I cannot extract the location data. Here is the server-side code I'm using to receive the data:

import socket

# Server address and port
server_ip = '192.168.1.14'
server_port = 12345

# Create a TCP server
server_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
server_socket.bind((server_ip, server_port))
server_socket.listen(1)

print('Waiting for vehicle positioning terminal connection...')

while True:
    # Accept client connection (blocking)
    client_socket, client_address = server_socket.accept()
    print('Vehicle positioning terminal connected:', client_address)

    # Receive data (102400 bytes = 100KB)
    data = client_socket.recv(102400)

    print('Received data:', data)
    # Attempt to decode (this will likely fail due to encryption)
    print('Decoded data (likely incorrect):', data.decode('latin-1', errors='replace')) # Added error handling

    # Close the client connection
    client_socket.close()

Running the above code, I periodically receive data like this:

<code>Received data: b'~\x01\x00\x00!\x01ea8f\x97\x00\x00\x00,\x01/70111kg-12a\x00\x000000000\x01\xd4\xc1b88888\xe5~'
Decoded data (likely incorrect): ~…!.../…011kg-12a…0000000…b88888e5~</code>

I have also attached a diagram showing the data transmission format. It appears the data is encrypted and a password is involved.

Solution

The vehicle positioning terminal's data is transmitted in binary format and appears to be encrypted. Here's a breakdown of how to approach this problem:

1. Incorrect Decoding: data.decode() is inappropriate for encrypted or custom-formatted data. You need the correct decoding method based on the device's protocol documentation.

2. Obtain the Device Protocol: The manufacturer's protocol documentation is crucial. It describes the data format and parsing instructions. The mention of a password suggests encryption.

3. Binary Data Parsing: Manually parse the binary data byte-by-byte, guided by the protocol. Example (assuming you know part of the format):

   data = b'~\x01\x00\x00!\x01EA8f\x97\x00\x00\x00,\x01/70111KG-12A\x00\x000000000\x01\xd4\xc1B88888\xe5~'
   
   # Example parsing (adapt to your actual protocol)
   header = data[:5]
   print("Header:", header)
   
   # Assuming device ID is next 10 bytes (ASCII)
   try:
       device_id = data[5:15].decode('ascii')
       print("Device ID:", device_id)
   except UnicodeDecodeError:
       print("Error decoding Device ID. Check encoding.")
   
   # ... continue parsing based on the protocol ...

4. Data Decryption: If encrypted, you need the encryption algorithm and key (likely the "password"). Consult the device documentation or manufacturer.

5. Specialized Libraries/Tools: The manufacturer might provide an SDK or library for data parsing.

In summary, you must obtain the device's protocol documentation and understand any encryption used to successfully parse the data. Providing more information about the device and its protocol will allow for more specific guidance. Consider adding error handling (like try-except blocks) to your parsing code to gracefully handle unexpected data. The latin-1 encoding in the original code was added for better error handling of the unknown encoding.

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