def _create_siv_cipher(factory, **kwargs):
 try:
  key = kwargs.pop('key')
 except KeyError as e:
  raise TypeError(('Missing parameter: ' + str(e)))
 nonce = kwargs.pop('nonce', None)
 return SivMode(factory, key, nonce, kwargs)

def _create_siv_cipher ( factory , ** kwargs ) : try : key = kwargs . pop ( 'key' ) except KeyError as e : raise TypeError ( ( 'Missing parameter: ' + str ( e ) ) ) nonce = kwargs . pop ( 'nonce' , None ) return SivMode ( factory , key , nonce , kwargs )
create a new block cipher .