A user of a mobile communications device may access services in a target domain using a source domain identity that is used to access services in a source domain. To enable such a use of the source domain identity in the target domain, the source domain identity may first be enrolled in the target domain. The enrollment may be facilitated by an enrollment entity at the target domain, such as a gateway or an OpenID server for example. The enrollment entity may establish a secure channel with the user's device for enabling enrollment of the source domain identity. Once enrolled, the source domain identity may be used for authentication of the user in the target domain. Enrollment of the source domain identity and/or authentication of the user based on the enrolled source domain identity may be implemented using a local OpenID provider (OP) residing on the user's device.