Abstract: In mobile IPv6 networks, when mobile user accesses from a foreign domain, the home domain and the foreign domain should coordinate to perform user authentication. The existence of inter-domain trust relationship among multiple domains is the prerequisite for implementing inter-domain user authentication. Current fast authentication methods in mobile IPv6 networks lacks consideration of inter-domain trust relationship when performing inter-domain user authentication. Authentication failure caused by untrustworthiness is not detected until the entire authentication procedure is over. A fast inter-domain authentication method combining trust mechanism for wireless mobile IPv6 networks is proposed, which considers inter-domain trust relationship between mobile user’s home domain and the access domain in the pre-handoff procedure and realizes effective mutual authentication between mobile user and the access domain in one round-trip. A dynamic maintenance mechanism for inter-domain trust relationship is also designed. Based on the combined public key algorithm, a signature and verification scheme is designed for network entities, which accelerates mutual authentication process. Theoretical analysis and numerical results show that the proposed method is more effective in reducing total authentication and handoff delay and the signaling overhead than relative methods. Also, based on the security of CPK algorithm, the method is sufficient for privacy and unforgeability in realizing mutual authentication in mobile IPv6 networks.