'Returns the byte string of the initialization vector for the encryption
scheme. Only the PBES2 stores the IV in the params. For PBES1, the IV
is derived from the KDF and this property will return None.
:return:
A byte string or None'

@property
def encryption_iv(self):

    encryption_algo = self[u'algorithm'].native
    if (encryption_algo in set([u'rc2', u'rc5'])):
        return self[u'parameters'].parsed[u'iv'].native
    octet_string_iv_oids = set([u'des', u'tripledes_3key', u'aes128_cbc', u'aes192_cbc', u'aes256_cbc', u'aes128_ofb', u'aes192_ofb', u'aes256_ofb'])
    if (encryption_algo in octet_string_iv_oids):
        return self[u'parameters'].native
    if (encryption_algo == u'pbes2'):
        return self[u'parameters'][u'encryption_scheme'].encryption_iv
    if (encryption_algo.find(u'.') == (-1)):
        return None
    raise ValueError(unwrap(u'\n                                                Unrecognized    encryption    algorithm    "%s"\n                                                ', encryption_algo))
