When you’re using digital services, you need to be sure that your privacy is being protected and your data is secure. Also institutions from higher education and research and service providers that offer services online need to know it is really you (and not someone pretending to be you), and to ensure your information is safe.
That is why some services require two-step authentication.
For those services you have to login using your institutional account and a second token (SMS, tiqr, YubiKey). This wiki contains more background information on how to log in with two-step authentication, how to register your token and how to replace or remove your token.