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


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)


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