I merged the LMIC 1.5 code with a different AES encryption module to fit the Atmega 328 Pro-Mini and probably the Uno as well. Discussed in topic HERE
Please have a look at: https://github.com/things4u/LoRa-LMIC-1.51
Probably tomorrow I will post an update to GitHub where I am making use of PROGMEM, which will give your sketch another 256 bytes of memory....
Maarten