Jean-Baptiste Bédrune (Sogeti / ESEC)

Presentation Title iPhone Data Protection in-Depth
Presentation Abstract

Smartphones contain valuable data and are a prime target for forensics investigators. The iPhone is no exception, and the technique introduced by Jonathan Zdziarski in 2008 can create a bit-by-bit copy of the phone data partition, by booting a custom ramdisk through BootROM DFU mode exploits, normally used for jailbreaking. This technique still works on newer devices like the iPhone 4, using the limera1n BootROM exploit released in October 2010 by geohot. Thus, with physical access to the phone, it is possible to extract lots of personal information, such as emails, pictures or text messages.

However, the data protection feature introduced with iOS 4 uses the phone passcode and device specific keys to secure master keys (class keys) protecting files and keychain items. We will describe the internals of the following iOS 4 features :

- Flash storage encryption / content protection
- Data wipe
- System keybag and escrow keybags
- Passcode derivation function
- Keychain storage

In order to retrieve all of the protected data, an attacker has to know the user passcode. The custom passcode derivation function used was designed to prevent off-device bruteforce attacks, by using the embedded hardware AES key (UID key).

We will demonstrate a simple bruteforce attack running off a custom ramdisk which results in complete bypass of an iPhone4′s security in less than 20 minutes

Note: Presenting with Jean Sigwald

About Jean-Baptiste Bédrune

Jean-Baptiste works at the Software security R&D team at Sogeti for 4 years. His domains of research include code (un)protection, audit of DRM solutions, applied cryptography, reverse engineering on embedded devices and distributed computing. Jean joined Sogeti in early 2010. His research topics include reverse engineering, embedded devices and smartphones security.

About Jean Sigwald

Jean Sigwald is a security researcher working at Sogeti ESEC R&D lab. His research is mainly focused on smartphones security and the services offered by the network operators.