otaa

OTAA, or Over-The-Air Activation, is a method to provision LoRaWAN devices onto a network. In OTAA, each device negotiates cryptographic keys with the network through a join procedure, rather than using a pre-programmed set of keys. This supports dynamic key management and easier provisioning.

Device stores DevEUI, JoinEUI, and a root key (AppKey). It sends a Join Request with DevEUI, JoinEUI, and a random DevNonce. The Network Server forwards the request to the Join Server, which, if valid, replies with a Join Accept containing a DevAddr and settings.

Upon Join Accept, the device derives two session keys from the AppKey and join parameters: NwkSKey for network security and AppSKey for application data. Once established, these keys secure future uplinks and downlinks.

OTAA provides stronger security and easier key rotation than Activation By Personalization (ABP), since keys are generated during join and are unique per session. It adds an extra message round-trip and increases reliance on the Join Server and network infrastructure.

In LoRaWAN, OTAA is a standard activation method, with ABP as an alternative. The join process is a cooperation among end device, Join Server, and Network Server, after which the device operates with its session keys until re-joined.