How to use ESP NOW local master key?

[somehibs]

ESP NOW offers set_pmk but doesn't offer a set_lmk. How do I set my lmk?

Master: set_pmk: 123, add_peer: (lmk: 555)
Slave: set_pmk: 123, set_lmk(lmk: 555)

ESP NOW doesn't have set_lmk. Master knows because he can add peer with lmk set. How does the slave know what his lmk is?

[lbernstone]

No idea, but doco is at esp-idf

[somehibs]

Yeah, I read the documentation. It was clear that you need to set an LMK for the PMK to be used during transmission, but it doesn't mention how to configure an LMK for the receiving device, so how does the receiving device decrypt the LMK packet? Both devices share a PMK, but only the transmitter knows the LMK.

Inside libespnow.a, you can find methods like mt_set_lmk. The documentation mentions an LMK configuration parameter that isn't available anywhere in the arduino-esp32 repository. Either mt_set_lmk needs to be exposed with a glue method like esp_now_set_lmk or arduino-esp32 needs to be able to set the build time LMK configuration. Or I'm misunderstanding what the LMK is used for.

[somehibs]

I've tried adding the receiver as a peer on both devices, with the LMK, MAC, channel and encrypt boolean set identically. The PMK for both devices is identical.

The sender states the message was sent successfully in the send callback, but the receiver does not decrypt or pass the message on to the recv callback. If I comment out the encrypt boolean, or set it to false, the receiver receives messages as normal, indicating my code is otherwise fine.

[lbernstone]

CSB. These are all esp-idf functions. You should submit this issue at esp-idf or take it to esp32.com for discussion.

[somehibs]

The issue is that the Arduino environment doesn't offer those methods.

[somehibs]

Well, whatever.