Ciphering on nanoBTS is depending on the installed software.

If you have a model 139/140 and the software is 120a... the A5/1 and A5/2
encryption is available;

120b... is A5/2 only and
120c... there is no encryption available.

When you have a model 108/110 the software should start with 119 and with
model 165 it starts with 168.