Multi-service residential access networks allow residential customers to choose amongst a variety of service offerings, over a range of Core Networks and subject to user requirements such as QoS, mobility, cost and availability. These issues place requirements on authentication for network access, with a need for mutual authentication of the residential gateway (RG) to the local access point (LAP). The EU-IST project TORRENT is building a testbed providing for multi-service residential access networks in order to demonstrate the benefit of intelligent control, both for the customer and for the network operators and service providers. Adequate security measures are essential in order to secure access to the TORRENT system and services and for QoS provisioning to authorised users. This paper examines the authentication issues for the TORRENT system and presents a public key based authentication protocol for mutually authenticating the RG and the LAP.