Abstract: A simple, efficient and reliable introduction of a service key into a terminal is made possible by a method for introducing a service key into a terminal where the terminal can use the service key to decrypt service data transmitted in encrypted form from a central control station via a public communication channel. The terminal stores a decoding key which is produced from an initialization value by a terminal programming device using an algorithm. The central control station uses an algorithm corresponding to the algorithm and initialization value in the terminal programming device in order to produce a coding key matching the decoding key. The service key stored in the central control station is coded using the coding key and is transmitted to the terminal where it is decoded using the stored decoding key.