Authentication in a packet data network

To packet date network data mobile node verification method, wherein a mobile node and telecommunications network data centre of which the mobile node and packet date network of secret secretly. The method, mobile node for transmitting user identity and program attack protection coding to the packet date network. The packet data obtaining network to confirm of ternary code, when using them to form a session key and a use and inquiry encrypting data rate of the session key to obtain a mobile node. The mobile node and can form an apparatus for coding unit by the searching and then forming session key. By the session key, a node of inspect for encrypting authentication code the validity. A verifying the code is correct, mobile node transmission responds the data packet code of the encryption for session key part, a verifying automatic to the packet date network.