Methods, systems, and computer program products for authenticating a mobile client that may have an input system optimized for numeric input. A mobile gateway receives authentication credentials from a mobile client and uses an authentication filter to map the authentication credentials according to pre-established criteria. The authentication filter may change the domain name, the username, or both. Then, the mapped authentication credentials are sent to a network that includes the content server being accessed. Any access privileges granted to the mobile client are based on the mapped authentication credentials. The mobile gateway may be configured to accept connections only from known servers. Mobile authentication credentials may be maintained in one or more domains, possibly having a trust relationship, or may be stored in a separately administered credential database.