This is the TAIT System Key Generator (aka TAIT syskey or TAIT system keygen).
It allows you to program trunking systems on the radio. You have to supply SysID and WACN and get the .tkey output.

It's simple and supports P25 Phase 1 and Phase 2 trunking on P25-capable radios like TP9100, TP9400, TP9600, TP9800, TP9900, TM9400, and TM9800.