Encrypting voice comunications..

[Tim Newsom]

If we have access to the mic and speakers while a call is in process, 
and we have the ability to record conversations etc...  Where does the 
processor sit in that chain?  Can we consume the voice, encrypt it and 
feed an encrypted datastream back out to the gsm module which would 
transmit it and another neo1973 user could receive the stream, process 
through decryption and play out?  OR is it more like a tap onto the mic 
and speaker lines where we can observe what's happening but not change 
the information transmitted to the gsm module?
--Tim