Encrypted Sender and Receiver Scripts

This example uses one sender and at least one receiver micro:bit.  Both micro:bit modules can be connected to a single computer, or to separate computers in the same room.

• Start with just two micro:bit modules.
• Open two separate instances of the micro:bit Python Editor.  
  • If both micro:bit modules are connected to the same computer, they can be two different tabs in the same browser. 
  • If they are connected to different computers, you will need one micro:bit Python Editor running on each computer.
• If you are in a classroom, pair up with another student and adjust the radio.config(channel=7) statements in both scripts.  Make sure that each pair of students is using a unique group number, from 0 to 83.
• Each pair should also update the xor_key from 42 to some value in the 1 to 255 range.
• Connect both micro:bit modules to USB ports.
• With the first micro:bit Python Editor, click Send to micro:bit to flash the Module 1: Sender Encrypted script to one micro:bit module.
• Click Show serial.
• With the second micro:bit Python Editor, Click Send to micro:bit to flash the Module 2: Receiver Encrypted script into one or more micro:bit modules.
• Click Show serial.

Module 1: Sender Encrypted

# Module 1: Sender

import radio

def get_input_string():
    print("Enter text:")
    return input()

def xor_encrypt(message, key):
    encrypted_message = ""
    for char in message:
        encrypted_message += chr(ord(char) ^ key)
    return encrypted_message

# Replace 'YOUR_XOR_KEY' with a value between 0 and 255
xor_key = 42

radio.on()
radio.config(channel=7)
radio.config(length=250)

while True:
    user_input = get_input_string()
    encrypted_message = xor_encrypt(user_input, xor_key)
    radio.send(encrypted_message)
    print("Sent:", user_input)

Module 2: Receiver Encrypted

# Module 2: Receiver

import radio

def xor_decrypt(encrypted_message, key):
    decrypted_message = ""
    for char in encrypted_message:
        decrypted_message += chr(ord(char) ^ key)
    return decrypted_message

def execute_python_code(script_lines, key):
    try:
        script = "\n".join(script_lines)
        exec(script)
    except Exception as e:
        print("Error:", e)

# Replace 'YOUR_XOR_KEY' with the same key used in the sender script
xor_key = 42

radio.on()
radio.config(channel=7)  # Set the same channel as the sender
radio.config(length=250)

script_lines = []
indent_level = 0

while True:
    encrypted_message = radio.receive()
    if encrypted_message is not None:
        try:
            decrypted_message = xor_decrypt(encrypted_message, xor_key)
            print("Received:", decrypted_message)

            if decrypted_message == "run":
                execute_python_code(script_lines, xor_key)
                script_lines = []
                indent_level = 0
            else:
                line_indent = len(decrypted_message) - len(decrypted_message.lstrip())
                if line_indent > indent_level:
                    script_lines.append(decrypted_message[indent_level:])
                else:
                    script_lines.append(decrypted_message)
        except Exception as e:
            print("Error decrypting message:", e)