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Apple and their elusive Full Disk Encryption solution
I have been researching how Apple has been implementing their full disk encryption control over the weekend and what I found puzzled me:
Although technically Apple provides a hardware full disk encryption solution, from a traditional security sense of the term, there is no full disk encryption available on the iPhone/Ipad currently! It sounds like a paradox? let me explain…
The closest analogy I can think of, would be if someone was selling you a house and claiming that the full house was protected with alarms in each room. The only problem, is that the alarm would only work when nobody was in the house… meaning the only protection your house effectively had was a simple front door key.
The following information can be found in the following article:
iPhone full disk encryption seems to have been implemented with one purpose in mind: fast/instantaneous remote wipe as it just erase the 256-bits encryption key.
Jonathan Zdiarski found that “the iPhone OS automatically decrypts data when a request for data is made, effectively making the encryption worthless for protecting data”
This is where the new iOs4.x “data protection” security feature comes into play, it allows for an app to derive a key from the user’s passcode/password and encrypt the app’s data. But so far it is only done by the built-in email app. APIs are available but each apps needs to use them if they want their data encrypted.
From the article referenced at the beginning of this post, I found the following two characteristics of that API the most interesting::
- Positive: There is a protection against brute force attack as an attacker can only guess about 20 passwords per second due to how keys are generated (which compares well to other software such as encrypted PGP files where 900 passwords can be guessed per second.)
- Negative: There is however a security weakness called the “Escrow Keybag, which is a collection of keys necessary to decrypt every file on the device without requiring the user’s password. This was done to allow computers to sync with the iPhone without asking the user for the password”. A company called ELCOMSOFT may be using this weakness in their iphone password recovery solution
The last point is of forensic significance. If both the iOS device and the computer used to sync it with are either seized or stolen then it is possible to find the plist/lockdown files on the computer and bypass the passcode used on the iOS device and dump all its data for analysis, unencrypted.
This is true for the latest iphones (3GS and 4G) with the latest firmware. For older model/versions there are other easier techniques to obtain the data.
Windows 7 is not better though:
Their might be some lights for Android based phone with the Motorola enterprise offering: http://www.networkworld.com/news/2010/100710-droid-pro-enterprise.html
The link below needs to be read with a warning as I don’t really agree with the author’s message that sounds as if all those phones are very secure and enterprise ready. They can be, but companies need to be aware of the limitations of the security controls that have been implemented. He still provides a good overview of each type of mobile phone capabilities (page 3) hence why I am providing the link:
Finally, those guys have a nice white paper on iphone forensics which was updated recently in November 2010:
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