public DeviceKeyId deviceKeyId() {
        String s = get(DEVICE_KEY_ID, null);
        return s == null ? null : DeviceKeyId.deviceKeyId(s);
    }
@Test
    public void testSetDeviceKeyId() {
        // change device key id
        SW_BDC.deviceKeyId(DEVICE_KEY_ID_NEW);
        assertEquals("Incorrect deviceKeyId", DEVICE_KEY_ID_NEW, SW_BDC.deviceKeyId());
        // clear device key id
        SW_BDC.deviceKeyId(null);
        assertEquals("Incorrect deviceKeyId", null, SW_BDC.deviceKeyId());
    }