The wireless network develop is support mobility within the Internet at presently. The mobile Internet use Mobile IP technologies in the wireless Internet. This paper is concerned with the security aspect of the registration protocol in Mobile IP. In this paper we publish a new method use the secure-key combine minimal public-key besides produce the communication session key in mobile node registration protocol. The all communication message are encrypt in our propose method. An easy and fast authentication method for establishing a mobile node's identity that can also prevent replay, TCP spicing and guessing attack is proposed.