I have an problem. because of UUID.
DESCRIPTION OF PROBLEM
I am a beginner developer. I have a one Issue about UUID. I using NSUUID().UUIDString and I saved in keychain but my managing director dosen't trust this api. he said that's not unique and we need unique key. Even wifi mac address or network mac address. so i told to him. "That's impossible. if you want to get unique key for ios device, you just use 'identifierForVendor().UUIDString' or 'NSUUID().UUIDString' and save in keychain. because in IOS only have a single key chain. But I made like that already." but he dosen't listen my opinion. Because I'm not engineer in Apple and just beginner. This is reason of who don't trust me. so please I need your formal reply. Or if you have another solution tell me about that. I need your help.
STEPS TO REPRODUCE
Create a UUID and store it in "keychain" and send the UUID to the server. Only up to two UUIDs can be registered on our server. If the number exceeds 2, the message "Device already registered" is displayed to the user. This situtation can possible when user use and install new device. For example if user install app where his third device can make situation like this.
This data is also stored in the "Realm.io"(mobile database).
This UUID data will not be lost if you save it to "KeyChain" even if you delete the app. So when the user re-installs the app, they can retrieve the previously saved UUID and re-use it and, if so our app never make a new UUID.
The problem is this. Some users say, "I own two devices, not just three, and I used this application well until yesterday, but suddenly I can not sign in, I get a pop-up window, and I see the message 'Device already registered.' I am thinking that the user is sharing the ID and password, but I can not prove it, I know it's just impossible because I tested the app before launch, but my supervisor does not trust me. He just instructs me to study the Apple manual or API reference for how to extract the wifi mac address or even the LAN card mac address even the CPU MAC Address.
But I already searched in Apple manual and Apple api reference document and Apple Forum and StackOverFlow. I know solution is only use code this what "UIDevice.currentDevice().identifierForVendor?.UUIDString" or "NSUUID().UUIDString ". So I just need to your formal reply for prove I'm not wrong. If am I wrong tell me another way.