old_contents: """
  Sending a message:
      Encrypt your plaintext with encrypt_message
      Your id will serve as your public key
  Reading a message
      Use decrypt_message and validate contents
  """
  
  from Crypto.PublicKey import RSA
  
  
  # Generates and writes byte string with object of RSA key object
  def create_key():
      key = RSA.generate(2048)
      f = open('key.pem', 'w')
      f.write(key.exportKey('PEM'))
      f.close()
  
  
  # Reads an exported key-bytestring from file and returns an RSA key object
  def retrieve_key():
      f = open('key.pem', 'r')
      key = RSA.importKey(f.read())
      return key
  
  
  def get_public_bytestring():
      key = retrieve_key()
      return key.publickey().exportKey()
  
  
  # Use own private key to decrypt broadcasted message
  def decrypt_message(message):
      key_obj = retrieve_key()
      return key_obj.decrypt(message)
  
  
  # Use given id to encrypt message
  def encrypt_message(key_string, message):
      key = RSA.importKey(key_string)
      return key.encrypt(message, 123)
new_contents: """
  Sending a message:
      Encrypt your plaintext with encrypt_message
      Your id will serve as your public key
  Reading a message
      Use decrypt_message and validate contents
  """
  
  from Crypto.PublicKey import RSA
  
  
  # Generates and writes byte string with object of RSA key object
  def create_key():
      key = RSA.generate(2048)
      with open('key.pem', 'w') as f:
          f.write(key.exportKey('PEM'))
  
  
  # Reads an exported key-bytestring from file and returns an RSA key object
  def retrieve_key():
      with open('key.pem', 'r') as f:
          key = RSA.importKey(f.read())
          return key
  
  
  def get_public_bytestring():
      key = retrieve_key()
      return key.publickey().exportKey()
  
  
  # Use own private key to decrypt broadcasted message
  def decrypt_message(message):
      key = retrieve_key()
      return key.decrypt(message)
  
  
  # Use given id to encrypt message
  def encrypt_message(key_string, message):
      key = RSA.importKey(key_string)
      return key.encrypt(message, 123)
  
subject: Use 'with ... as ...' for file opening. Standardize variable names.