1

I'm trying to create a LoRaWAN network with multicast using TTN. I have followed several videos and accessed anything I could find, but fundamentally it seems I cannot understand concept behind the keys.

My point of reference is https://lora-alliance.org/resource_hub/lorawan-remote-multicast-setup-specification-v1-0-0/ and video: https://youtu.be/qpnjOjHTCDc

I have successfully send Payloads on fport 200 and received the correct responses from my device, but when I schedule a downlink message to the MC group on say fport 1, nothing is received at the device. My end device is an STM32WL nucleo.

Info on my device after boot:

AppKey: 2B:7E:15:16:28:XX:XX:XX:XX:XX:XX:XX:XX:CF:4F:3C
NwkKey: 2B:7E:15:16:28:XX:XX:XX:XX:XX:XX:XX:XX:CF:4F:3C
AppSKey: 2B:7E:15:16:28:XX:XX:XX:XX:XX:XX:XX:XX:CF:4F:3C
NwkSKey: 2B:7E:15:16:28:XX:XX:XX:XX:XX:XX:XX:XX:CF:4F:3C
DevEUI: 00:80:E1:15:05:00:5D:C7
AppEUI: 01:01:01:01:01:01:01:01
DevAddr: 05:00:5D:C7

After OTAA JOIN +EVT:JOINED

MCRootKey: 7D:F7:6B:0C:XX:XX:XX:XX:XX:XX:XX:47:B9:1B:54:6F
MCKEKey: 8C:B8:66:5E:XX:XX:XX:XX:XX:XX:XX:E4:8A:19:27:7C
AppSKey: D0:B5:EE:1D:XX:XX:XX:XX:XX:XX:XX:CF:1B:8B:45:1E
NwkSKey: 0F:83:21:17:XX:XX:XX:XX:XX:XX:XX:DE:E5:C9:17:79
DBIntKey: 7A:C4:7C:65:XX:XX:XX:XX:XX:XX:XX:35:19:F8:9C:8E
DevEUI: 00:80:E1:15:05:00:5D:C7
AppEUI: 01:01:01:01:01:01:01:01
DevAddr: 26:0C:92:DF

After sending McGroupSetupReq (0x02)

ID : 0
McAddr : 260CA2A7
McKey : C0-27-FE-A2-XX-XX-XX-XX-XX-XX-XX-XX-51-98-A3-8B
McFCountMin : 0
McFCountMax : 10
SessionTime : 2541666257
SessionTimeT: 32768 s
Rx Freq : 869525000
Rx DR : DR_3

My Setup on TTN (as a multicast device/group) TTN Setup

Question1: Both references above refer to "McKey_encrypted" ... where is this key derived from? and what method can be used to derive MCRootKey and McKEKey?

Question1.1: Why do these already exist on my end device?

Question2: What keys should be taken from the multicast device/group created on TTN and put on the device

Question3: What keys should be taken from the device and put on the multicast device/group on TTN

Question4: What keys should be common on devices that will be part of the multicast?

Question5: Which is the key that should be included in the McGroupSetupReq command (if you can use any keys references above)

0

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Browse other questions tagged or ask your own question.