A chip card needs to be allocated in a secured manner to a network operator via a personalization center in order to determine a final authentication key which is attributed to a subscriber of the operator without its being transmitted via a network. The following is loaded into a card by a module: an algorithm and an allocation key; an algorithm for determination of the authentication key and at least one intermediate authentication key. A module transmits an allocation message which includes a final identity number, a random number and an allocation signature from the center to the card. The card authenticates the message by means of the allocation algorithm as a function of the allocation key and the allocation signature, and determines the final authentication key as a function of the intermediate key and the random number.