Backdoor is somewhat of a misconception. What they want are two front doors, ie we encrypt your message with the recipients public key, and we make a copy with our(in this case apple's) public key. We send both messages over the internet, and apple or your isp/cell service provider (we can also assume nsa prism has it too) stores the apple key'd message or both. When the government wants access, they can issue a subpoena for information from the isp/cell provider for the encrypted data (or just download it from Saratoga Spings), then they issue a warrant to apple to decrypt it with their private key. This is likely the only reasonable and responsible outcome that I can see resulting from this debate. Or, pessimistically it becomes an issue for political fodder and we leave it up to politicians who have little to no understanding of the technology to devise some technologically inept solution.