iPhone Attack Reveals Passwords In Six Minutes

angry tapir writes "Researchers in Germany say they've been able to reveal passwords stored in a locked iPhone in just six minutes and they did it without cracking the phone's passcode. The attack, which requires possession of the phone, targets keychain, Apple's password management system. Passwords for networks and corporate information systems can be revealed if an iPhone or iPad is lost or stolen."

Comments

Apple iOS File System Encryption

[jallen02]

In IOS >4 with a modern device (3GS or better, iPad included) this article is blatantly incorrect.

"The attack works because the cryptographic key on current iOS devices is based on material available within the device and is independent of the passcode, the researchers said.". Not true. In iOS4 they use a variant of PBKDF2 to generate an encryption key that is used along with the device key alluded to in this article to decrypt "class keys". The class keys are then used to access data at the various protection levels (Never, After First Unlock, Only When Unlocked). Each of those levels of data has a separate key. Those keys are required to decrypt the individual keys on each file. Each file has an encryption key set on it in the meta data (which means you do have to reformat your system and set a reasonable passcode).

Because of the PBKDF2 variant brute forcing is infeasible. Because of the device key you have to try this IN the device and are limited to Apple's hardware for forcing.

All of this is possible because Apple has an AES-256 hardware chip that blazes through crypto for that algorithm.

Remote wipe uses yet another key (the file system key). So each file encryption key requires a "Class key" and a "file system key" to be decrypted. Lose either one and the file system is history. So remote wipe is accomodated in newer versions of iOS by just forgetting the file system key.

In short, this article is not providing an accurate portrayal of "current/latest" devices. Though I am not sure how many people: Have the newer hardware, have iOS 4 AND have reformatted their filesystem to accomodate the required metadata.

Re:Apple iOS File System Encryption

[jallen02]

I feel I should clarify. The article summary is a bit misleading and the paper is not, exactly, misleading.

In the version of iOS they tested you have the option of encrypting your keychain entries using the mechanism I describe (which means they would come us as "protected"). And as the PDF article mentions they could not extract the device key (forcing a local brute force attack if you want the passcode set for the device). If the protection level is set to encrypt the keychain entry with the device passcode it can't be recovered through some flaw in the encryption (that we know about).

So the article is basically saying, "Gee we can access things that aren't flagged to be protected with the device passcode". Which is, well what any reasonable observer expected since that is exactly how it was described over a year ago. It is good to see a working implementation.

Apple's real flaw here is that they did not force this encryption for *everything*. Instead they rely on developers to pass in certain options when storing keychain entries (and or when writing files to disk). Without these options the data is, sadly, recoverable. Apple even only encrypts the Mail app out of the box, which does not set the best example. That said they are basically making a very technical commentary on design decisions by Apple and I think this point gets lost in all the scare mongering. It would have been much more coherent (but not have gotten as much PR) to simply make this clear straight away.