I have to create an app that makes me the intermediater between two people talking through SMS. All messages have to go via me and the sender and receiver should not know each-other's identity. If I use a platform wherein I have millions of users and I have to send thousands of messages every second, How do I can facilitate this? I tried generating random numbers for each pair of sender and receiver, it was a costly affair. Can someone please suggest an easier way? It has to work for very basic phones, Users typing the unique numbers has to be completely avoided. Each user has a unique username.