A lighting device for communication with a mobile terminal, comprising: a lighting means, and an electronic operating device for operating the lighting means, a data storage unit, in which a first key is stored in a memory area reserved therefor, an encryption unit configured to read out the first key from the reserved memory area and, in accordance with a specifiable encryption operation, to convert measurement value data and/or identification data intended for transfer to the mobile terminal into a message encrypted by means of the first key, and a transmitting unit configured to transmit the encrypted message to the mobile terminal.