I'm going to take Dino's word over that of the people supplying forensics tools to LEOs: a 5-character alnum passphrase on iOS takes years to brute force. The actual filesystem on an iPhone is encrypted under a key encrypted by (IIRC) a key derived from the PIN.
Well, then you are wrong. @JZdziarski, aka Jonathan Zdziarski, aka NerveGas, is a former member of the "iPhone Dev Team", a group (which I am currently part of) that focuses on "jailbreaking" the iPhone (removing the restrictions on its usage and allowing third party software to run on it).
Let's put it this way: it is absurd to believe that the iPhone's filesystem is encrypted with the PIN number. When the phone turns on, it is already booted up, and applications like MobileMail, Skype, and Latitude are already in the background running with your data. You can receive text messages and phone calls, which are stored as notifications and in the appropriate databases: you don't need to unlock it first.
Meanwhile, none of the jailbreaking tools (which often operate while the phone is in "DFU" mode, after it has been rebooted and without any other human interaction) require you to type in your PIN, yet make tons of filesystem modifications to both partitions (the system one with the firmware from Apple, and the user partition with the data for each user), which should be a pretty obvious clue that you don't need anything from the user to get access to any of that data.
Instead, all of the data is simply encrypted with a key derived from the device, which therefore means that all you need is "virtually any exploit" on the device, whether it be userland (send a fancy SMS message to the device which crashes CommCenter or SpringBoard) or bootloader (attacking it over USB in DFU mode, stealing the keys directly; something we currently can do for all Apple devies but the iPad 2), in order to get access to the personal data (even stuff you recently deleted, of course, due to how filesystems work) which is on it.
> 5-character alnum passphrase on iOS takes years to brute force.
No, it doesn't. That's only 60 million combinations. Writing the code would take longer than the brute force search. Of course, there are already commercial applications that do all that.
