> They bought a hack from another company for an old model of phone. If the case had been involving the latest model handset, the vendor claimed they had not yet (but were confident they would) hack it.
There is actually an important distinction to make here too.
When you have something like Secure Boot, whose purpose is to make the device trustworthy to enter your passphrase into, it's completely impossible. You don't know if the device you're using is actually the same device, you don't know if someone is watching you, the thing it claims to do is not a thing it can actually accomplish.
But Apple does something separate from that. They have tamper-resistant hardware for storing keys, so that the hardware can store a strong key and enforce a maximum number of guess attempts for a weaker password/PIN.
The disadvantage of this is that it's pure attack surface compared with using a strong passphrase to begin with. If you have a strong passphrase the attacker has to break the encryption. If you have a weak PIN for hardware protecting a stronger key the attacker can break the encryption or break/backdoor the hardware or guess the weak PIN before hitting the maximum number of attempts.
The advantage is of course that it lets you use a PIN instead of a long passphrase, but there is also something else. That hardware doesn't need root. All it needs is to store a key while the device is locked and then spit it back out if you give the right PIN and erase it if you make too many bad attempts. No part of that inherently requires it to be at ring -3. It can be completely independent from all of that.
> And if the device is tamper-resistant?
That's the problem with Secure Boot -- it doesn't matter. Stealing your passphrase by recording it is an attack that can be pulled off by a middle schooler with a nanny cam. It's easier to do that than to backdoor the firmware on a non-tamper-resistant computer, which at least requires you to know what "firmware" is. So what attack are we actually preventing at the cost of having untrusted and potentially vulnerable code at ring -3?