> As it is, my iPhone unlock PIN is everything that's needed to decrypt the data server-side
That's not quite true. They use a HSM on their datacenters, which only allows a limited amount of guesses. They only allow a limited amount of guesses, before your data is wiped forever[1].
Technically, the keys are in the processor's state. You are just trusting that it won't divulge the keys without a correct PIN. You are also trusting the processor is properly secured. And you are trusting that no one would go through the effort to extract the keys physically with scanning probe microscopy or something.
One must also understand that you're wrong. My threat model isn't Apple. My threat model is
a) Overreaching law enforcement, which want to take a look at what I'm up to.
b) Data breach at Apple exposes all my data
c) Errors where my pictures gets in another users photo album, as seen on Google Photos once.
That's not quite true. They use a HSM on their datacenters, which only allows a limited amount of guesses. They only allow a limited amount of guesses, before your data is wiped forever[1].
[1] https://blog.cryptographyengineering.com/2021/03/25/whats-in...