input: Write a function to create an application in Python for encryption and decryption of strings. The application should take a string as input, use the AES cipher algorithm in ECB mode for encryption, and return the encrypted result. Similarly, it should take an encrypted string as input and return the decrypted result.
  assert encrypt(b'This is a test message')==b'E\x880\x05\xbb\xa8\x1b\xfa\xea\xb43\xeb\xc2Gpq'
  assert decrypt(b'E\x880\x05\xbb\xa8\x1b\xfa\xea\xb43\xeb\xc2Gpq')==b'This is a test message'
output: from Crypto.Cipher import AES
  import base64
  
  def encrypt(message):
      key = b'Sixteen byte key'
      cipher = AES.new(key, AES.MODE_ECB)
      padded_message = message + b'\0' * (AES.block_size - len(message) % AES.block_size)
      encrypted = cipher.encrypt(padded_message)
      return encrypted
  
  def decrypt(encrypted_message):
      key = b'Sixteen byte key'
      cipher = AES.new(key, AES.MODE_ECB)
      decrypted = cipher.decrypt(encrypted_message)
      return decrypted.rstrip(b'\0')