dav
Data Protection is implemented by constructing and managing a hierarchy of keys, building on the hardware encryption technologies built into Apple devices. It's controlled on a per-file basis by assigning each file to a class; accessibility is determined by whether the class keys have been unlocked.
The four protection classes, from strongest to weakest:
NSFileProtectionComplete — Files are only accessible when the device is unlocked.
NSFileProtectionCompleteUnlessOpen — A file can only be opened when the device is unlocked, but is not closed when the device is locked — it's encrypted when the last open handle is closed. Suitable for data being uploaded in the background.
NSFileProtectionCompleteUntilFirstUserAuthentication — The resource cannot be accessed until after the device has booted. After the user unlocks the device for the first time, the app can access the resource and continue to do so even if the user subsequently locks the device. Fortify This is commonly called AFU (After First Unlock). This is the default class for all third-party app data not otherwise assigned to a Data Protection class.
NSFileProtectionNone — The resource has no special protections. It can be read or written at any time. The encryption only uses a key derived from the device's UID.
The BFU/AFU Distinction — The Heart of the Signal Issue
Apple's iOS devices operate in two key security states that directly impact data accessibility: Before First Unlock (BFU) and After First Unlock (AFU).
When an iPhone is in the BFU state, it has been powered on or rebooted but not yet unlocked with a passcode. In this state, the Secure Enclave does not release the decryption keys needed to access most user data.
Once you've unlocked once (AFU), files protected with NSFileProtectionCompleteUntilFirstUserAuthentication become accessible, the Keychain is available, and background processes and apps can access encrypted content as needed.
The Signal notification content issue connects here because notification data (including previews) stored in the default CompleteUntilFirstUserAuthentication class remains decryptable by any process — including OS-level forensic tools — as long as the phone has been unlocked at least once since the last reboot.
1. The three C’s: Clarity always, Consistency with determination, Concision when prudent. 2. Keep the pain in the right place. 3. Fight entropy!
So in the context of the main example in this article, I would say you can try to improve clarity by e.g. wrapping the existing auth code in something that looks nicer in the context of your new endpoint but try very hard to stay consistent for all the great reasons the article gives.
Tests very much in particular deserve more weight. Being DRY is nowhere on the same level as bike shedding code style.
"Various studies around the world have proposed different explanations, such as economic status. Lower income is associated with greater declines. One study looked at use of computer games among young people [as a possible explanation]. Some folks have tracked declines in alcohol use, and we know that [alcohol use] can be associated with disinhibition. We have seen, somewhat, [an] increase in sex toy use—from what we looked at, not a massive increase. If there is a change, it’s probably just going to contribute to one of the blips. I don’t expect it to be the explanation."
I suggest the book Defy Aging by Beth Bennett for a HN level deep dive into the science.
Where Mathematics Comes From: How the Embodied Mind Brings Mathematics into Being by George Lakoff
I like it. Some UX tweaks would be nice, maybe an undo, a clear all, and perhaps some helpful focus shifting (of which tile is being intended for a click) depending on context.
I'm on PopOS.