UWB communication node and operating method

1. An ultra-wideband communication node, comprising:

an ultra-wideband communication unit configured to transmit one or more messages to a plurality of external responder nodes and to receive one or more responses from said responder nodes;

a processor configured to use a common cryptographic session key to encrypt said messages, wherein said common cryptographic session key is a key shared between the ultra-wideband communication node and all the external responder nodes;

wherein the processor is further configured to use responder-specific cryptographic session keys to decrypt the responses and/or to encrypt further messages to the responder nodes, and wherein each individual one of said responder-specific cryptographic session keys is a key shared between the ultra-wideband communication node and one of the external responder nodes.

2. The communication node of claim 1 , comprising a further communication unit which is configured to transmit the common cryptographic session key and the responder-specific cryptographic session keys to the respective external responder nodes.

3. The communication node of claim 2 , wherein the further communication unit is a Bluetooth communication unit, a Wi-Fi communication unit or a cellular communication unit.

4. The communication node of claim 1 , further comprising a secure element, wherein the common cryptographic session key and the responder-specific cryptographic session keys are stored in said secure element.

5. The communication node of claim 1 , wherein the ultra-wideband communication unit is further configured to receive identifiers from the external responder nodes, wherein said identifiers uniquely identify the external responder nodes, and wherein the processor is further configured to use the identifiers to retrieve responder-specific cryptographic session keys from the secure element.

6. The communication node of claim 1 , wherein the messages are multicast messages or broadcast messages.

7. The communication node of claim 1 , further comprising an authentication unit configured to perform a mutual authentication process with the external responder nodes.

8. The communication node of claim 1 , wherein the messages and the responses include scrambled timestamp sequences and payloads.

9. The communication node of claim 1 , wherein the common cryptographic session key and the responder-specific cryptographic session keys are usable for a single communication session or for a limited number of communication sessions.

10. The communication node of claim 1 , wherein the processor is further configured to:

generate a new common cryptographic session key and new responder-specific cryptographic session keys after one or more communication sessions have ended;

share said new common cryptographic session key and new responder-specific cryptographic session keys with the responder nodes, wherein the new common cryptographic session key is shared with all the responder nodes and each new responder-specific cryptographic session key is shared with a specific one of said responder nodes.

11. A communication system comprising the communication node of claim 1 and the plurality of responder nodes, wherein each one of said responder nodes is configured to:

use the common cryptographic session key to decrypt messages received from the communication node;

use the responder-specific cryptographic session key that has been shared with the respective responder node to encrypt responses to said messages and/or to decrypt further messages received from the communication node.

12. The communication system of claim 11 , wherein the communication node is configured to carry out ranging operations with the responder nodes, and wherein said ranging operations include one or more of said messages and one or more of said responses.

13. A method of operating an ultra-wideband communication node, comprising:

transmitting, by an ultra-wideband communication unit comprised in the communication node, one or more messages to a plurality of external responder nodes and receiving, by said communication unit, one or more responses from said responder nodes;

using, by a processing unit comprised in the communication node, a common cryptographic session key to encrypt said messages, wherein said common cryptographic session key is a key shared between the ultra-wideband communication node and all the external responder nodes;

using, by said processing unit, responder-specific cryptographic session keys to decrypt the responses and/or to encrypt further messages to the responder nodes, wherein each individual one of said responder-specific cryptographic session keys is a key shared between the ultra-wideband communication node and one of the external responder nodes.

14. The method of claim 13 , further comprising transmitting, by a further communication unit comprised in the communication node, the common cryptographic session key and the responder-specific cryptographic session keys to the respective external responder nodes.

15. The method of claim 14 , wherein the further communication unit is a Bluetooth communication unit, a Wi-Fi communication unit or a cellular communication unit.

16. The method of claim 13 , wherein the communication node further comprises a secure element, and wherein the common cryptographic session key and the responder-specific cryptographic session keys are stored in said secure element.

17. The method of claim 13 , wherein the ultra-wideband communication unit further receives identifiers from the external responder nodes, wherein said identifiers uniquely identify the external responder nodes, and wherein the processing unit uses the identifiers to retrieve responder-specific cryptographic session keys from the secure element.

18. The method of claim 13 , wherein the messages are multicast messages or broadcast messages.

19. The method of claim 13 , wherein the method is implemented in a computer program comprising executable instructions stored in a non-transitory computer-readable medium, wherein when the executable instructions are executed by a processing unit, cause said processing unit to perform the steps of the method.