a lot of iPhone apps also try to collect information from the environment they are running in to try and fingerprint a user. this can be used to track a user ev

a lot of iPhone apps also try to collect information from the environment they are running in to try and fingerprint a user. this can be used to track a user even when the apps do not share keychain access. this article on nshipster has a good summary of the technique: https://nshipster.com/device-identifiers/ https://nshipster.com/device-identifiers/ i've seen extremely high quality fingerprinting being used by some apps and they are going to extreme lengths to hide the collection of this data from apple or other interested parties. over 48 bits of entropy being recorded which should uniquely identify users.