I just received an email message from Apple stating that my two-step authentication would change over to two factor authentication when I install iOS 11. I understand why this change is being made, but I have a concern. I enabled the old two-step authentication back when it was a new feature and generated a recovery key. I memorized this recovery key because I only had an iPhone at the time and entering the recovery key was the easiest way for me to authenticate a new device. Now, however, there seems to be no recovery key with the new two-factor authentication. Suppose I only have one trusted device, an iPhone, and the only trusted phone number is connnected with that device. How am I to authenticate that single device with the new two factor authentication? If I ever need to erase my iPhone, how do I sign into this iPhone if I own no other Apple devices? I'm deaf and using a once telephone would mean that I would need to trust another person with the security of my iCloud account and that isn't going to happen. Can I somehow generate a new recovery key with the new two factor authentication like I did with the two step auth?