Methods, devices, and computer programs for an authentication of a user to a service of a service provider are disclosed. Access for the user to the service of the service provider is requested. One or more authentication security profiles are selected by the service provider for specifying an authentication security requirement of the service provider for the authentication of the user to the service. An indication of the one or more selected authentication security profiles and a user identity identifying the user to an identity provider are sent from the service provider to the identity provider for requesting the authentication of the user by the identity provider. The user is authenticated based on the user identity and one of the one or more selected authentication security profiles. An assertion indicating the authentication of the user to the service provider is sent to the service provider.