Serial.println("\nEncryption/Decryption Test:");
  String plaintext = "This string is encrypted with AES-256 in Cipher Block Chaining mode!"; // String to be encrypted
  int iv[16]; // Initialization vector
  for (int i = 0; i < 16; i++){
    iv[i] = random(256); // Fill iv array with random numbers. I suggest you use a more secure method of random number generation!!!
  }
  encrypt_string_with_aes_in_cbc(plaintext, iv); // Function for encryption. Takes the plaintext and iv as the input.
  Serial.println("\nCiphertext");
  Serial.println(string_for_data);
  String ciphertext = string_for_data; // Back the ciphertext up
  decrypt_string_with_aes_in_cbc(ciphertext); // Decrypt data
  Serial.println("Plaintext:");
  Serial.println(string_for_data);