Method for securing data traffic in a mobile network environment

A method in a mobile network environment for securing data traffic between an external network and a terminal of a mobile user coupled to the external network, wherein the mobile user can be authenticated in a home location network by way of a private home location key pair, the method which comprises:

• a) producing a private external key pair by exchanging partial keys between the terminal and a data securing device of the external network;
• b) transmitting from the data securing device to the home location network an item of key information based on at least one of the partial keys and a message certified by the terminal by way of a first home location key of the private home location key pair;
• c) verifying the certification of the message in the home location network with a second home location key of the private home location key pair, and producing a certificate for the key information;
• d) transmitting the certificate to the data securing device;
• and
• e) accepting the private external key pair for securing the data traffic subject to verification of the certificate transmitted from the home location network.