CROSS REFERENCE

The present application claims the benefit under 35 U.S.C. 119 of German Patent No. DE 102018217964.6 filed on Oct. 19, 2018, which is expressly incorporated herein by reference in its entirety.

FIELD

The present invention relates to a method for monitoring data communications in a communication system, which includes a plurality of subscribers and has a communications medium (shared medium) jointly usable or shared by the subscribers.

The present invention also relates to a device for implementing such a method.

BACKGROUND INFORMATION

Conventional methods and devices for monitoring data communications generally require special hardware and/or complex signal processing.

SUMMARY

An object of the present invention to improve a method and a device for monitoring data communications is to reduce or prevent the disadvantages of the related art.

Preferred specific embodiments of the present invention include a method for monitoring data communications in a communications system, which includes a plurality of subscribers and has a communications medium jointly usable by the subscribers (or shared (in particular, among the subscribers)); the method including the following steps: ascertaining the subscribers of the communications system; forming a first collection, in particular, e.g., a list, of possible messages, which may be sent by at least one of the ascertained subscribers via the communications medium; ascertaining messages sent via the communications medium; evaluating the ascertained messages. During the evaluation of the ascertained messages, which, therefore, have actually been sent via the communications medium, the first collection may be advantageously considered, which means that ascertained messages may be compared, for example, to the first collection. This allows efficient monitoring of the data communications in the communications system; in particular, the monitoring not requiring any expensive, special hardware or complex signal processing. On the contrary, the knowledge characterized by the first collection is advantageously used; the knowledge possibly being available during the construction of the communications system and/or being ascertainable then or later without much effort.

“Subscriber” or “subscriber device” is presently understood as any technical device or any technical system, which is configured or suited to enter into data communication with other subscribers via the (shared) communications medium, thus, for example, to send and receive messages via the communications medium to and from one or more other subscribers, respectively. If the communications system includes, for example, a CAN bus, the above-mentioned subscriber and/or the subscriber device may have, for example, a CAN transceiver for data communications via the CAN bus.

In further preferred specific embodiments, it is provided that the method further include the following steps: a) ascertaining a transmission state of at least one ascertained subscriber, preferably, of a plurality of, or of all the ascertained subscribers; b) for the at least one ascertained subscriber, preferably, for the plurality of, or all of the ascertained subscribers, ascertaining a second collection of possible messages, which may be sent via the communications medium, by the at least one, or the plurality of, preferably, by all of the ascertained subscribers, as a function of the specific transmission state of the ascertained subscriber in question; in particular, the evaluating of the ascertained messages being carried out as a function of the second collection. This renders possible particularly precise monitoring of the data communications.

In further preferred specific embodiments, the second collection is updated, preferably repeatedly; in particular, the second collection being updated a) periodically and/or b) as a function of a, preferably, current transmission state of the at least one ascertained subscriber, and/or c) as a function of at least one ascertained message.

In further preferred specific embodiments, it is provided that the evaluating include: in the ascertained messages, checking if at least one message is present, which is not included in the second collection. This may indicate, for example, a manipulation attempt (e.g., injection of the message by an attacker).

In further preferred specific embodiments, it is provided that the evaluating of the ascertained messages include: ascertaining a frequency of the messages sent by at least one particular, ascertained subscriber (in particular, ascertaining the frequency of messages of the same type; in the case of CAN bus systems, e.g., ascertaining a frequency of messages having the same CAN ID).

In further preferred specific embodiments, it is provided that the evaluating of the ascertained messages additionally include the following steps: comparing the ascertained frequency to a frequency specified for the particular, ascertained subscriber (and/or for the relevant message type (e.g., CAN ID); and, optionally, initiating an error response, if the ascertained frequency does not agree with the frequency specified for the particular, ascertained subscriber (and/or for the message type in question).

In further preferred specific embodiments, it is provided that the evaluating additionally include: checking if the ascertained frequency falls below a specifiable, first threshold value and/or exceeds a specifiable, second threshold value and/or is identical to zero; and, optionally, initiating an error response, if the ascertained frequency falls below the specifiable, first threshold value and/or exceeds the specifiable, second threshold value and/or is identical to zero.

In further preferred specific embodiments, an error response may generally be initiated, e.g., if a collection is checked against communications or messages on the network, and if, in this context, e.g., at least one anomaly is detected.

In further preferred specific embodiments, it is provided that the method include the following steps: checking if all of the messages transmittable by a particular subscriber are contained in the ascertained messages; deducing a manipulation attempt, if not all of the messages transmittable by the particular subscriber are included in the ascertained messages; in particular, deducing a manipulation attempt, if not all of the messages transmittable by the particular subscriber are contained in the ascertained messages within a specifiable waiting time. In further preferred specific embodiments, the specifiable waiting time may be monitored with the aid of a timer.

In further preferred specific embodiments, it is provided that the method include the following steps: checking if messages transmittable by a particular subscriber are contained in the ascertained messages; deducing a manipulation attempt, if some, but not all of the messages transmittable by the particular subscriber are included in the ascertained messages. This advantageously allows, e.g., communications or messages actually occurring to be compared to expected communications or messages for each subscriber. If, e.g., all of the communications of a subscriber are absent, this indicates its complete malfunction. If only a portion of the communications of a subscriber are absent, this indicates an attack (masquerade).

Further preferred specific embodiments relate to a device for monitoring data communications in a communications system, which includes a plurality of subscribers and has a communications medium jointly usable by the subscribers; the device being configured to execute the following steps: ascertaining the subscribers of the communications system; forming a first collection of possible messages, which may be sent by at least one of the ascertained subscribers via the communications medium; ascertaining messages sent via the communications medium; evaluating the ascertained messages.

In further preferred specific embodiments, it is provided that the device be configured to execute the method in accordance with the specific embodiments.

Further preferred specific embodiments relate to a subscriber or a subscriber device (e.g., CAN transceiver, in the case of a CAN bus system) for a communications system, which has a shared communications medium jointly usable by a plurality of subscribers; the subscriber having at least one device according to the specific embodiments.

Further preferred specific embodiments relate to a communications system, which includes a (shared) communications medium jointly usable by a plurality of subscribers, as well as at least one subscriber according to the specific embodiments and/or at least one device according to the specific embodiments; in particular, the communications system taking the form of a CAN (controller area network) system or CAN FD (flexible data rate) system.

Further preferred specific embodiments relate to use of the method according to the specific embodiments and/or of the device according to the specific embodiments and/or of the subscriber according to the specific embodiments and/or of the communications system according to the specific embodiments, for monitoring the communications system for a fault and/or for manipulation of at least one subscriber.

Further advantageous refinements of the present invention are described herein.

The example embodiments according to the present invention may advantageously allow manipulation of the communications system and/or of at least one subscriber to be detected efficiently, without the provision of additional hardware, in particular, special hardware. In particular, this allows so-called man-in-the-middle attacks and/or masquerading attacks to be detected.

Additional features, uses and advantages of the present invention ensue from the following description of exemplary embodiments of the present invention, which are illustrated in the figures. In this context, all of the described or illustrated features form the subject matter of the present invention, either alone or in any combination, irrespective of their combination, wording or representation in the description herein and in the figures.

