Operating method for an automation system, - wherein the automation system comprises at least one automation unit and a plurality of automation servers (11, 11'), - wherein the automation servers (11, 11') are connected to the automation unit via a communication network, - wherein the automation servers (11, 11') communicate with the automation unit using a certificate of the automation unit which has been communicated to them, - wherein the automation servers (11, 11') validate the certificate of the automation unit prior to communication with the automation unit, - wherein the automation unit controls an installation part of an industrial technical installation (1, 1') according to the communication with the respective automation server (11, 11'), - wherein the automation servers (11, 11'), in order to validate the certificate, on the one hand check a chain of trust of the certificate and on the other hand check a validity of the certificate by accessing a black list, - wherein the black list is stored at a storage location and a reference to the storage location is contained in the communicated certificate, characterised in that - the automation system additionally comprises a central management unit, which is connected to the automation servers (11, 11') and the automation unit via the communication network, - the central management unit, in order to enable the communication of the respective automation server (11, 11') with the automation unit, communicates the respective chain of trust to the respective automation server (11, 11'), - the central management unit, in order to prevent the communication of a respective automation server (11, 11') with the automation unit, revokes the respective chain of trust from the respective automation server (11, 11') or prompts a certificate of the automation unit, which has been valid until this point in time, to be entered into the black list and - the central management unit only communicates the respective chain of trust to a respective automation server (11, 11') when it has revoked all chains of trust determined for communication with the automation unit from all other automation servers (11, 11') beforehand, or has prompted a certificate of the automation unit, which has been valid until this point in time, to be entered into the black list, or the certificate of the automation unit is otherwise invalid. - wherein the automation system comprises at least one automation unit and a plurality of automation servers (11, 11'), - wherein the automation servers (11, 11') are connected to the automation unit via a communication network, - wherein the automation servers (11, 11') communicate with the automation unit using a certificate of the automation unit which has been communicated to them, - wherein the automation servers (11, 11') validate the certificate of the automation unit prior to communication with the automation unit, - wherein the automation unit controls an installation part of an industrial technical installation (1, 1') according to the communication with the respective automation server (11, 11'), - wherein the automation servers (11, 11'), in order to validate the certificate, on the one hand check a chain of trust of the certificate and on the other hand check a validity of the certificate by accessing a black list, - wherein the black list is stored at a storage location and a reference to the storage location is contained in the communicated certificate, - the automation system additionally comprises a central management unit, which is connected to the automation servers (11, 11') and the automation unit via the communication network, - the central management unit, in order to enable the communication of the respective automation server (11, 11') with the automation unit, communicates the respective chain of trust to the respective automation server (11, 11'), - the central management unit, in order to prevent the communication of a respective automation server (11, 11') with the automation unit, revokes the respective chain of trust from the respective automation server (11, 11') or prompts a certificate of the automation unit, which has been valid until this point in time, to be entered into the black list and - the central management unit only communicates the respective chain of trust to a respective automation server (11, 11') when it has revoked all chains of trust determined for communication with the automation unit from all other automation servers (11, 11') beforehand, or has prompted a certificate of the automation unit, which has been valid until this point in time, to be entered into the black list, or the certificate of the automation unit is otherwise invalid.