Abstract: A process and a device which are characterized in that at least one first security device is arranged at one subscriber, that at least one second security device is arranged in the exchange, or alternatively, an additional device with at least one second security device is connected upstream from each exchange, the first and the second security devices being able to encode and/or decode and exchange with each other connection establishment and/or service information of the subscriber.

Abstract: A device for authenticating subscribers to one or more exchanges of a digital communication network having at least one subscriber-side network terminator, to which at least one data terminal may be connected. It is a distinction of the invention that provision is made at every subscriber for at least one first authentication module capable of receiving a first identification carrier, and provision is made in the exchange for at least one second authentication module capable of receiving a second identification carrier, or that, alternatively, connected between the network terminators assigned to the exchange and the exchange is an additional device, in which is arranged a second authentication module capable of receiving a second identification carrier, the authentication modules being capable of encoding and/or decoding a piece of information with an individual, subscriber-specific key and of exchanging information with each other for unilateral and/or bilateral authentication.