This application discloses a mobile network authentication method, a terminal device, a server, and a network authentication entity. The method includes: receiving, by a first terminal device, a DH public key and a first ID that are sent by at least one second terminal device; sending a first message to a server, where the first message includes a DH public key of each second terminal device of the at least one second terminal device and a first ID of the second terminal device; receiving a second message sent by the server, where the second message includes a DH public key of the server and a second ID of the second terminal device that is generated by the server; and sending, by the first terminal device, the second ID of the second terminal device and the DH public key of the server to the second terminal device.