Abstract: The invention relates to a method for restricting the access to data of group members of a service subscriber group. Group members of a service subscriber group are each assigned an identifier. The data of the group members are assigned to the identifier in each case and the data of the group members are stored in a data memory (DS2) of a group management computer (GR) which manages the service subscriber group. Applying the method, a first group member requests a service, providing the identifier of a second group member, the performance of said service requiring the data of the second group member. The identifier of the second group member is sent to the group management computer, which verifies whether the requested service using the data of the second group member is authorized, and in the case where an authorization exists the data of the second group member are sent to a service computer (DR1) controlling the performance of the requested service.

Abstract: The invention relates to a method for the authorization of payments in a communication network. According to said method, when a pay service is requested by a communication terminal of a service user, an authorization message is sent to a payment service provider by said communication terminal, authorizing payment for said service. An individual authorization ID is stored by the payment service provider in a memory, the authorization ID is sent to the service provider device, a payment request message containing the authorization ID is sent to the payment service provider, and the payment is recognized as authorized by the payment service provider if the authorization ID of the payment request message is available in the memory.

Abstract: A method for preparing a payment transaction using a communication terminal associated with a payer and a receiver terminal associated with a payee. The communication terminal is associated with a first payment system in a first communication network and the receiver terminal is associated with a second payment system. In this case, a payment request message relating to the payer from the receiver terminal prompts the second payment system to create authorization data associated with the payment request message and to send them to the receiver terminal. The receiver terminal transmits a further payment request message together with the authorization data to the first payment system. The first payment system uses the authorization data to check whether the payee is authorized to participate in the payment transaction, and if appropriate the first payment system transmits a guarantee data record guaranteeing payment by the payer to the receiver terminal.