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A comment on Why does iPhone 13 screen replacement disable Face ID. Parent comment

Re:Why does iPhone 13 screen replacement disable Face ID by josephcsible on Saturday October 02, 2021 @04:12PM (#28731654)
Under what circumstances exactly would it be a safety or security issue to replace one genuine OEM part with another genuine OEM part, identical in all ways except for the serial number?
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Re:Why does iPhone 13 screen replacement disable Face ID by Zak on Saturday October 02, 2021 @04:33PM (#28731839)
It's a safety issue to replace some, but not all of the cells in a Li-ion battery with cells that are not the same age and condition. Since smartphone batteries are almost always a single cell, it's a non-issue.

Another scenario I can imagine is a charge controller reducing the maximum charging current as the battery ages based on information stored in the controller's memory, which would be incorrect if the cell is replaced. Of course, it would be unusual to replace a cell with one in worse condition, so it would also be surprising for that to be a safety concern.

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Re:Why does iPhone 13 screen replacement disable Face ID by gambiting on Saturday October 02, 2021 @04:57PM (#28732010)
Keep in mind that the check done inside an iPhone doesn't prevent the failure mode you describe. After all the phone only checks the microcontroller attached to the battery, not the actual cells(if that's even possible in any way).
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Re:Why does iPhone 13 screen replacement disable Face ID by Zak on Saturday October 02, 2021 @06:50PM (#28732810)
> not the actual cells(if that's even possible in any way).

It isn't, but there are some controller circuits that switch off permanently if the voltage falls out of range, making changing cells more difficult.

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Re:Why does iPhone 13 screen replacement disable Face ID by loopback_device on Saturday October 02, 2021 @04:30PM (#28731822)
Perhaps to prevent (or at least make it harder for) someone shorting around the security it is supposed to provide, i.e. by emulating or modifying the replacement part - not that that'd really stop the determined ones
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Re:Why does iPhone 13 screen replacement disable Face ID by theranger on Saturday October 02, 2021 @05:53PM (#28732421)
It would not be a safety issue indeed only until the replacement part includes some mitm hardware that tampers the face id authentication flow. And this can be planted into the genuine looking replacement part as well.
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Re:Why does iPhone 13 screen replacement disable Face ID by josephcsible on Saturday October 02, 2021 @06:00PM (#28732485)
I expect that at least one of these things would have to be true:

1. The MITM hardware could be installed into the screen that's already paired with the iPhone, so the serial check wouldn't help

2. The MITM hardware would make the screen look non-genuine regardless of serial, so the serial check wouldn't be needed

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Re:Why does iPhone 13 screen replacement disable Face ID by xondono on Saturday October 02, 2021 @05:08PM (#28732103)
It wouldn’t, OEM batteries can be swapped with no issues, it’s non-genuine parts what causes issues.
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Re:Why does iPhone 13 screen replacement disable Face ID by l4yao on Saturday October 02, 2021 @05:14PM (#28732143)
On iPhone 12 and moreso on 13, many genuine OEM parts cannot be swapped by anyone other than those authorized by Apple.
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Re:Why does iPhone 13 screen replacement disable Face ID by xondono on Saturday October 02, 2021 @05:29PM (#28732244)
AFAIK, that’s only the case for the screen, and there’s a warning when swapping the rear camera.
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Re:Why does iPhone 13 screen replacement disable Face ID by philliphaydon on Saturday October 02, 2021 @09:44PM (#28733841)
https://youtu.be/8s7NmMl_-yg

It’s not just a warning. Functionality is flat out disabled. Swapping parts between 2 iPhone 13s boinks them.

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Re:Why does iPhone 13 screen replacement disable Face ID by l4yao on Saturday October 02, 2021 @08:24PM (#28733421)
(Some) Functionality is also lost on the front camera, faceid sensor and battery.
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