[FedCom] P-25/DG protocol question

[HornSmoke]

Q: Normal repeaters usually will have a PL/DPL tone, at least on the 
input for obvious reasons. In the P-25 world, is there a practice of 
assigning key and or some such thing that keeps other P-25 radios from 
inadvertently broadcasting, or cross-channeling? For example, on analog 
repeaters the "tone" adds a thin layer of protection from idiots 
"kerchunking." If so, is it like encryption where an actual key or 
algorithm is used?

Loren