A method for outputting confidential data via an output device of a landline telephone , comprising: - providing the confidential data in a first data-processing device which is assigned to a service provider, wherein the confidential data are assigned to a personalized data-processing operation in the first data-processing device ; - storing the confidential data in a storage device , from which at least the first data-processing device is capable of retrieving data; - providing secret data which represent a secret agreed upon between the service provider and a person to whom the personalized data-processing operation is assigned, in the first data-processing device ; - transmitting message data from the first data-processing device to a second data-processing device , which is assigned to a message service provider and is configured to transmit received message data to one or more landline telephones in a network of landline telephones, wherein the message data comprise the following: - the confidential data, - the secret data and - receiver data which indicate a landline telephone in the network of landline telephones as receiving device; - querying the secret via the landline telephone in response to an evaluation of the message data by the second data-processing device ; - receiving user input data in the landline telephone via an input device of the landline telephone; - transmitting the user input data from the landline telephone to the second data-processing device ; - evaluating the user input data by the second data-processing device ; - transmitting the confidential data from the second data processing device to the landline telephone , if it is determined during evaluation that the user input data correctly indicate the secret agreed upon between the service provider and the individual; and - outputting the confidential data via an output device of the landline telephone . - providing the confidential data in a first data-processing device which is assigned to a service provider, wherein the confidential data are assigned to a personalized data-processing operation in the first data-processing device ; - storing the confidential data in a storage device , from which at least the first data-processing device is capable of retrieving data; - providing secret data which represent a secret agreed upon between the service provider and a person to whom the personalized data-processing operation is assigned, in the first data-processing device ; - transmitting message data from the first data-processing device to a second data-processing device , which is assigned to a message service provider and is configured to transmit received message data to one or more landline telephones in a network of landline telephones, wherein the message data comprise the following: - the confidential data, - the secret data and - receiver data which indicate a landline telephone in the network of landline telephones as receiving device; - the confidential data, - the secret data and - receiver data which indicate a landline telephone in the network of landline telephones as receiving device; - querying the secret via the landline telephone in response to an evaluation of the message data by the second data-processing device ; - receiving user input data in the landline telephone via an input device of the landline telephone; - transmitting the user input data from the landline telephone to the second data-processing device ; - evaluating the user input data by the second data-processing device ; - transmitting the confidential data from the second data processing device to the landline telephone , if it is determined during evaluation that the user input data correctly indicate the secret agreed upon between the service provider and the individual; and - outputting the confidential data via an output device of the landline telephone . <EOS>