Actually there is some standardization activity trying to do this. It does not solve the main problem: if you let the originating carrier sign the caller id, yo

Actually there is some standardization activity trying to do this. It does not solve the main problem: if you let the originating carrier sign the caller id, you still have to trust that carrier to really check if the caller is authorized to use it. Number portability prevents you from using certificates older than 24h.