Network and application session keys the same among all my ABP devices

[arjanvanb (Arjan)]

@TD-er

As far as I know, the DevAddr is only used with OTAA, to generate a session key.

Nope. It’s also present in every uplink and downlink message, for both ABP and OTAA devices. And it’s used when calculating the MIC, along with other details such as the frame counter.

@TD-er

I guess it can be detected when two nodes send using the same session key at the same time

The session keys are not part of the message, but the MIC is. However, validation of the MIC starts with a list of all devices of a given DevAddr, and that’s not the same for all devices in this case. See also How does a network know a received packet is for them? - #2 by htdvisser

@TD-er

I would suggest to generate unique ABP keys per node

For security: yes, absolutely. But I doubt this problem is caused by using the same secrets. And if it is: the messages should be visible in the gateway’s log then, if one has access to that. (For many gateways the Traffic page in TTN Console is not working right now.)

@TD-er

So if you disable the frame counter check, in the console, you will be able to see those “duplicate” messages again.

Aside: in an earlier, meanwhile deleted, topic @verdiagriculture wrote that the frame counter checks were disabled. Also the number of messages per day is low, so no problems to be expected with, e.g., 16 bits counters.