Method for transmitting personal data, wherein the method comprises the following steps: receiving a request, which is represented by an electrical signal, from a sensor device for recording personal data via a sensor interface of a group of watchdog devices (104, 106, 18, 110) to the sensor device; producing (-203) an encryption key and shares (134, 136, 138, 140) of a decryption key by using the group of watchdog devices (104, 106, 18, 110), in response to the reception of the request, wherein the decryption key is split into the shares (134, 136, 138, 140) by using a method for secret sharing, and one of the shares (134, 136, 138, 140) is assigned to each one of the group of watchdog devices (104, 106, 18, 110); providing the encryption key to the sensor device via the sensor interface; providing the shares (134, 136, 138, 140) of the decryption key to a terminal device via a terminal interface of the group of watchdog devices (104, 106, 108, 110) to the terminal device; the sensor device generating encrypted personal data by using the personal data and the encryption key; receiving the encrypted personal data via an input interface of a data board device to the sensor device; and providing the encrypted personal data via an output interface of the data board device to the terminal device; characterized in that the encrypted personal data are provided with a unique pointer, which is an index or the result of a hash function on the encrypted personal data, and the method comprises a step of blocking the provision of the shares (134, 136, 138, 140) of the decryption key to the terminal device if a check on the pointer by the group of watchdog devices (104, 106, 108, 110) reveals that the personal data have already been sold to another terminal device. receiving a request, which is represented by an electrical signal, from a sensor device for recording personal data via a sensor interface of a group of watchdog devices (104, 106, 18, 110) to the sensor device; producing (-203) an encryption key and shares (134, 136, 138, 140) of a decryption key by using the group of watchdog devices (104, 106, 18, 110), in response to the reception of the request, wherein the decryption key is split into the shares (134, 136, 138, 140) by using a method for secret sharing, and one of the shares (134, 136, 138, 140) is assigned to each one of the group of watchdog devices (104, 106, 18, 110); providing the encryption key to the sensor device via the sensor interface; providing the shares (134, 136, 138, 140) of the decryption key to a terminal device via a terminal interface of the group of watchdog devices (104, 106, 108, 110) to the terminal device; the sensor device generating encrypted personal data by using the personal data and the encryption key; receiving the encrypted personal data via an input interface of a data board device to the sensor device; and providing the encrypted personal data via an output interface of the data board device to the terminal device; characterized in that the encrypted personal data are provided with a unique pointer, which is an index or the result of a hash function on the encrypted personal data, and the method comprises a step of blocking the provision of the shares (134, 136, 138, 140) of the decryption key to the terminal device if a check on the pointer by the group of watchdog devices (104, 106, 108, 110) reveals that the personal data have already been sold to another terminal device.