OK it aint mirc related. I figured that some of you bright cookies might find an answer anyway.

I have a p2p network. I have central 'account keeping' servers, whcih provide a SOAP interface, basically a database with security.
The p2p network is made up of VoIP clients. The VoIP clients send data back and forth, and make OUTSIDE phone calls.
What I want to do is think of a way of assigning credit to a client's account whenever they make an outside phonecall for someone else.
Trouble is, this is all opensource whichc means that any encryption/checksums etc i do to make sure data isn't faked are all known, and theoretically easily faked by simply compiling a different version fo the client.
CAN anyone suggest a way, without using my server's precious bandwidth, to assign credit to client's accounts in a way that is NIGH ON impossible to fake.