In the rapidly expanding mobile environment, authenticity of communicating parties is one of the big research challenges and is receiving increasing attention. In the Mobile IPv6 defined by IETF (Internet engineering task force), IPSec (IP security) protocols and RR (return routability) mechanism are used to protect signaling between related communicating nodes, however, how to realize identity authentication has not been efficiently solved. In this paper, the advantages and disadvantages of two authentication techniques?certificate-based authentication and identity-based authentication are analyzed. The scalability of certificate-based means is excellent, but the deployment of PKI (public key infrastructure) and the distribution of certificates make this method costly. On the contrary, identity-based method hurdles the deficiency of certificate-based means, nevertheless the scalability suffers from the share of parameters among related nodes. Then an approach of integrating the two methods mentioned above is proposed to realize a secure and fast authentication with low cost and high scalability. Finally, this hybrid technique is applied in Mobile IPv6 to improve the negotiation of SA (security association), and the security issues are discussed.