It is disclosed a method and a bootstrapping client (33) for assuring that a particular user (31) is present at local user authentication. It is also disclosed a method and a network application function (36) for authenticating a generic authentication architecture, GAA, client (34) to network application function, NAF (36). In addition, the NAF (36), requiring that the presence of the authorized user should be confirmed, sends a Nonce denoted as Nonce_UI, in which UI stands for “User Involvement”. The Nonce_UI indicates explicitly that the user involvement is required.