Communication system comprising a central data processing device, access stations and external stations, and incorporating a cryptographic check against falsification of an external station, and external stations for use in such a communication system

摘要

A communication system comprises a central data processing device (30) and a number of access stations (20, 46) which are coupled thereto. Also provided are a number of external stations (26, 46, 50) which can be selectively coupled to the access stations. An external station is validated in that encoded data is applied to the access station. After decoding and a further encoding operation, the data is returned to the access station. Therein, the data is decoded again and compared with the data originally formed for encoding.