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iOS 11.4 to Make iPhones Harder to Crack

Digital forensics firm Elcomsoft has discovered that betas of iOS 11.4 include a “USB Restricted Mode” that makes it impossible to extract data from an iOS device after it has been locked for 7 consecutive days. The company is uncertain of the exact mechanism:

At this point, it is still unclear whether the USB port is blocked if the device has not been unlocked with a passcode for 7 consecutive days; if the device has not been unlocked at all (password or biometrics); or if the device has not been unlocked or connected to a trusted USB device or computer. In our test, we were able to confirm the USB lock after the device has been left idle for 7 days. During this period, we have not tried to unlock the device with Touch ID or connect it to a paired USB device. What we do know, however, is that after the 7 days the Lightning port is only good for charging.

Elcomsoft speculates that this feature is a response to firms like Grayshift that provide iPhone-cracking tools to law enforcement (see “Thoughts on Tim Cook’s Open Letter Criticizing Backdoors,” 17 February 2016).

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Comments About iOS 11.4 to Make iPhones Harder to Crack

Notable Replies

  1. I’m almost tempted to ask, should USB access to the phone be possible at all without TouchID? I’m not sure I’m aware of any situation where I hook up my iPhone to my Mac and I’m not able to quickly authenticate with TouchID. Considering the privacy implications (Grayshift) I wouldn’t mind being super restrictive about it at all.

    I wonder why Apple appears to have chosen 7 days. Personally, I’d want to chose something a lot shorter. A user setting for this would be nice, but that apparently isn’t Apple’s style (there are a gazillion prefs for social media related stuff and “sharing” yet that doesn’t seem to be an issue, guess I’m just a dinosaur).

    Anyway, I actually do think it’s a bit excessive that about once every 5 or so days TouchID breaks — especially because it usually happens at the worst possible moment — because I need to manually enter my passphrase. I guess I’m just surprised that seems to be required more often (or at least as often) as authenticating before USB syncing would (assuming the feature gets implemented the way it’s being reported).

  2. This is almost certainly a response to the grey box cracking machine on sale to law enforcement.

    An interesting issue if you leave your phone at home while on vacation, or indeed the iPad, we have older models which lay unused for weeks at a time. I wonder about visitors to the house or children using old passwords repeatedly. Tricky.

  3. TouchID is less secure than the passcode, but that’s an interesting idea.

  4. I’m not sure I see the issue. Those circumstances don’t require USB access, do they? And if it is, USB access is reenabled the moment you put in your passcode, isn’t it?

  5. I wasn’t clear, the worry is forgotten passcodes.

  6. Ah. I see.

    But once a week or so my phone requires me to put in my passcode anyway before TouchID will work again.

    I’m pretty sure that if you completely forget the passcode, the only solution right now is to reset the phone (erasing it). Law enforcement has figured out a way around that and Apple is trying to close that hole. So far, so good.

    The only question is how/whether you will be able to erase the phone after the 7days.

  7. I think requiring use of touch id would be unwise. I probably know more people with iPhone’s who don’t use Touch ID than do. They prefer to enter a passcode simply because whenever they have setup and attempt to use Touch ID, it works so poorly for them that they find it faster to just use a passcode. But some still use USB to backup to iTunes so requiring Touch ID would be an irritant for them.

  8. I guess the problem is that TouchID or FaceID are quick whereas entering a 16-character passphrase takes forever. Especially on a tiny software KB.

    Sure, a possible solution to that is to fall back to simple 4-digit numeric passcodes. Especially those easy to type (1-1-1-1 duh), but that can hardly be a serious recommendation these days. ;)

  9. Depends on the user, of course, but I would like to see the time-out be much shorter. I jokingly, but only slightly, suggested 7 days was a typo for 7 minutes. But in all seriousness, I don’t see any reason it should be that long since the counter resets when a password is provided. Maybe it should simply be tied to the TouchID timeout?

    And as for very long iOS passwords, I will remind people again that checking (decrypting) the password must be done on the phone, and that processes is gated at 1 check for 80ms. So a 6 character numeric password taxes days to crack (and only represent 10^6 passwords). An 8 digit alpha numeric (62^8) takes half a million years, and that is only using A-Z, a-z, and 0-9.

    Add in a single “special” character like % or { and you’ve taken the search pool from 62 characters to about 95 (the common ASCII characters someone might use) and the amount of time up into the 15-30 million years range.

    So if you are typing in a 20 character random password into your iPhone you are technically many orders of magnitude more secure than my 10 characters one, but not in any meaningful way. (my password represents an integer followed by 11 zeros number of years to check all possible passwords and yours is an integer followed by 30 zeros number of years).

    And these numbers annoy get shorter because the phone cannot process the check faster and the check cannot be done off the phone.

  10. Do Grayshift and any similar device speed up the process or just bypass the “erase after 10 failures” feature. If it doesn’t speed it up then it’s hard to see the utility of it for law enforcement unless it’s a 4 character code.


  11. They do not, which is why a 6 digit pin takes days (it would only take about 24 hours on the phone, but it reportedly takes them 3-4 days, so whatever they are doing to avoid the 10 attempt lockout makes the process much longer).

    Most people have a 4 or 6 digit PIN.

  12. I’m not clear on this. Does this mean that if you don’t use your iDevice running iOS 11.4 for 7 days, Apple will brick it? Or will it still work if you power it up and enter your password?

  13. Probably not, but since it’s in beta, nobody who knows is allowed to confirm or deny that it’s even a feature, and if it is it could change before release, so we’ll all just have to wait and see.


  14. Yes, absolutely. I want to continue to be able to plug my iPhone into my car’s head unit and have it play media without having the phone constantly unlocked within a reasonable time that it was last unlocked. (I could use Bluetooth and just charge with USB, but the sound quality is noticeably worse.) I love the idea of a data lockout of USB after a period of time, or after you force a passcode unlock requirement (rapid press the sleep button five times on a Touch ID phone, or squeeze the sleep and volume button for a few seconds.)

  15. I wasn’t thinking it should constantly re-lock. What I was thinking was that it would require TouchID once when you plug it into you car’s USB for the USB audio connection to work. From then on, as long as it remains plugged in it will work.

  16. I still don’t like the idea of using Face ID to authenticate before playing music in the car (as I don’t use Touch ID, I would have to be looking at the phone to unlock it at the proper angle.) I think a seven day timeout is fine; even two or three days would be fine. And it’s not just car audio systems; I can just imagine people howling about plugging lightning earbuds into their iPhone 7/8/X and not having music play until they actually unlock the phone when that doesn’t happen with BT headphones or traditional headphone jacks on iPhone 6/6s/SE… It sounds like a mild annoyance, but I think most people would howl about that.

  17. I’m very happy about this. But it should be noted it’s optional. If once every hour ist too often, you have the option to turn it off.

  18. There is no reason to turn it off, however.

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