Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Why can't Apple decrypt your iPhone?

blog.cryptographyengineering.com

Post reply on HN
Print view View original

21–30 of 132 posts

Re: Why can't Apple decrypt your iPhone?

#21

Post by giovannibajo1 »

nemothekid wrote: post #11
vexelized wrote: post #8

What about iCloud? It used to be that a user could reset their password and then restore from iCloud backup on a new phone... Is this no longer true?

From what I can understand, if you wanted to hypothetically maximize your security, it would mean turning off iPhone backups. Apple could also have it set that you must have the iPhone passphrase to restore a backup but obviously those can be "easily" brute forced (because for the restore to work, it must mean you can bypass the old device's UID)

You can still fully backup your phone through iTunes, if you want to avoid iCloud backups, until those get encrypted as well.

Re: Why can't Apple decrypt your iPhone?

#22

Post by lisper »

weinzierl wrote: post #13
lisper wrote: post #9

Earlier quoted context omitted.

This is the fundamental problem: unless you are rolling your own silicon, at some point you have to take some big corporation's word for it that a chip does what they say it does. This fundamental problem is the reason that nuclear launch codes are protected by a relatively low-tech solution: http://en.wikipedia.org/wiki/Gold_Codes

But if this is the case, why bother with bullet point 1. to 4. The chip is probably manufactured in China, why spend a thought about whether US law enforcement can somehow via Apple decrypt the data of my phone when the Chinese Government can do it anyways?

1-4 from the original article are based on the premise that the iPhone is in fact as secure as Apple claims it is, and tries to reverse engineer how that could be done. Your point #5 is a possible way that the phone could in fact be insecure despite 1-4. My point is that unless you have your own silicon foundry you have no choice but to trust someone, or resign yourself to the possibility that your iPhone may not be secure despite what Apple says.

Re: Why can't Apple decrypt your iPhone?

#23

Post by JoshTriplett »

Now if only it was possible to turn off remote installation of applications on both iOS and Android devices, this kind of security would actually mean something.

Right now, you can do full disk encryption on an Android device (which seems likely to become hardware-assisted on future devices similar to the solution mentioned in the article). If you pick a sufficiently strong passphrase, that should keep your data secure even on devices without hardware assistance. However, if the device is turned on and locked (the common case), it's trivial to remote-install an arbitrary app, including one that unlocks the phone. (You can do this yourself with your Google account, which means anyone with access to that account can do so as well.)

It would help to be able to disable remote installation of any kind; that wouldn't have to come at the expense of convenience, because the phone could just prompt (behind the lockscreen) to install a requested app.

Re: Why can't Apple decrypt your iPhone?

#25

Post by icebraining »

JoshTriplett wrote: post #23

Now if only it was possible to turn off remote installation of applications on both iOS and Android devices, this kind of security would actually mean something. Right now, you can do full disk encryption on an Android device (which seems likely to become hardware-assisted on future devices similar to the solution mentioned in the article). If you pick a sufficiently strong passphrase, that should keep your data secu…

As far as I know, it can install an app but not run it (EDIT: on Android, that is). So it shouldn't be able to do any such decryption.

Re: Why can't Apple decrypt your iPhone?

#26

Post by RexRollman »

JoshTriplett wrote: post #23

Now if only it was possible to turn off remote installation of applications on both iOS and Android devices, this kind of security would actually mean something. Right now, you can do full disk encryption on an Android device (which seems likely to become hardware-assisted on future devices similar to the solution mentioned in the article). If you pick a sufficiently strong passphrase, that should keep your data secu…

I've been thinking about the possiblity of commercial software updates being used as an attack vector to overcome WDE. Could you imagine if the NSA went to Apple or Microsoft and said "push this compromising update to computers from this IP address/MAC address/serial number"?

Re: Why can't Apple decrypt your iPhone?

#27

Post by comex »

> The Secure Enclave is designed to prevent exfiltration of the UID key. On earlier Apple devices this key lived in the application processor itself, and could (allegedly) be extracted if the device was jailbroken and kernel patched.

Speaking as a jailbreaker, this is actually incorrect. At least as of previous revisions, the UID key lives in hardware - you can ask the hardware AES engine to encrypt or decrypt using the key, but not what it is. Thus far, neither any device's UID key or (what would be useful to jailbreakers) the shared GID key has been publicly extracted; what gets extracted are secondary keys derived from the UID and GID keys, but as the whitepaper says, the passcode lock key derivation is designed so that you actually have to run a decryption with the UID to try a given passcode. Although I haven't looked into the newer devices, most likely this remains true, since there would be no reason to decrease security by handing the keys to software (even running on a supposedly secure coprocessor).

Re: Why can't Apple decrypt your iPhone?

#29

Post by comex »

[deleted] wrote: post #24
venomsnake wrote: post #16

So the key is derived from passcode? isn't that 5 digits that are easy to brute force?

[deleted]

> Also, it's my understanding that authentication can be trivially bypassed if the phone is kept powered on? (ie. authentication data is stored in memory? Seems to be the case for at least Touch ID)

It can be bypassed if the phone is kept powered on -and someone is able to start running code on it-. The normal approach of Apple signing a malicious recovery/update image would require rebooting first; there are probably exploits to be found somewhere, but Apple probably doesn't have any intentional mechanism for running code without either rebooting or unlocking the phone (at which point a lot more services open up including developer tools, etc.).

Also, Touch ID expires after a while, and (edit: I said the key is probably wiped, but that makes no sense if the phone continues to display contact names and such on the lock screen; there may be details in Apple's white paper, but since I don't remember any, disregard.)

Re: Why can't Apple decrypt your iPhone?

#30

Post by opendais »

icebraining wrote: post #25
JoshTriplett wrote: post #23

Now if only it was possible to turn off remote installation of applications on both iOS and Android devices, this kind of security would actually mean something. Right now, you can do full disk encryption on an Android device (which seems likely to become hardware-assisted on future devices similar to the solution mentioned in the article). If you pick a sufficiently strong passphrase, that should keep your data secu…

As far as I know, it can install an app but not run it (EDIT: on Android, that is). So it shouldn't be able to do any such decryption.

The problem is the attack surface for an app on a device vs. in the wild is much, much larger and much, much less secure.

Once its on your phone, it can just screenshot things if nothing else.

Post reply on HN