[naturalauction]

One approach on iOS is to store unique identifier in the “Keychain” (or iCloud itself) which is data kept in the cloud tied to a user’s Apple ID account. Of course this is only an impediment to a determined stalker (who could create a new Apple ID). But a determined stalker could also use a fake name and get a new phone number.

See https://stackoverflow.com/questions/25276393/how-to-ban-an-i... for more details.

[gruez]

>One approach on iOS is to store unique identifier in the “Keychain” (or iCloud itself) which is data kept in the cloud tied to a user’s Apple ID account

Wouldn't it be obviously visible because you can see the app/file on icloud?

Also, I'm pretty sure the keychain idea is banned by app store guidelines.

[yreg]

Haha, the funny thing is that the service isn’t even storing that piece of data – the user is! So GDPR, etc. should be covered.

Although, if the user finds out about the mechanism they can just delete the entry from their keychain.

[newZWhoDis]

That keychain is different from the publicly viewable one in settings