void setup() {
  // put your setup code here, to run once:
  Serial.begin(9600);

  char message[] = "Hello, World!"; // original message
  char key = 'K'; // encryption key

  int len = strlen(message);

  for (int i = 0; i < len; i++) {
    message[i] = message[i] ^ key; // XOR operation with key to encrypt character
  }

  // After execution, the contents of the message will be encrypted
  Serial.println(message);
}

void loop() {
  // put your main code here, to run repeatedly:
}