OTAA - Over The Air Activation
ABP - Activation By Personalisation
It refers to the way the keys required for encryption are acquired. With ABP these are set when provisioning the device and will be reused after a reboot which makes communication less secure. With OTAA the keys are exchanged (secure) when the device (re)‘joins’ the network, every join uses new keys.
N.B. couple of hints for those new to LoRaWAN:
- To prevent replay attacks LoRaWAN uses frame counters. The node starts with 0 on power on, the back-end stores the last seen value. So for ABP to nodes packets will be ignored until the frame counter exceeds the value stored in central database. For OTAA the join procedure resets the counters in the database to 0 so all transmissions will be considered new and valid.
For people insisting on using the less secure ABP, there is a checkbox in the node details to disable the frame counter check. The network will still ignore packets with the same counter and data, considering it duplicate data. (Which means resetting the counter after each transmission while sending static data does not result in data for your application) - When using OTAA there is no need to rejoin the network every X amount of time, the node stays joined as long as it keeps track of the keys exchanged during the join and the ‘current’ frame counters.