Re: ipads/iphones and full disk encryption

[Tim Doty <tdoty () MST EDU>]

On Wed, 2011-10-12 at 14:44 +0000, Youngquist, Jason R. wrote:
> As many of you know, ipads/iphones and other devices are being
> introduced into the corporate and educational institution environment.
> Currently we require all institutional owned laptops to be encrypted
> using full disk encryption.  The Apple ipad/iphone supposedly has
> “full disk encryption” but I’ve done a bit of googling and it appears
> that the encryption is really all that it is cracked up to be (see
> reference URLs below).  So, I’m wondering how other organizations are
> addressing this threat – specifically since a number of high-level
> folks seem to be carrying ipads with them these days with potentially
> sensitive information on them.
>
>  
>
> I would appreciate any thoughts on this issue.

It is popular to take pokes at Apple's encryption, but with iOS4 (at
least on iPhones and I believe iPad2) the encryption is approximately as
strong as the password that is set.

If there is no password/passcode -- then it provides the same protection
as having a PKI private key that is not password protected; in other
words, none.

If there is a password/passcode set then it is approximately as good as
the password. The typical 4 digit PIN is trivially defeated in a brute
force.

Another issue is you mention "full disk encryption". No iOS device has
full disk encryption, and I doubt comparable devices (e.g., running
android) do either. If you've read Zdiarski's work then you should know
that there are two partitions, one encrypted and one not. (Ah, you only
linked to blurb blog posts, not the actual information as to
implementation weakness so you may not be aware of the distinction.)

Another point to consider is where the device is synced and how it is
synced. Apple gets blasted for the default backups not being encrypted
-- but they also are stripped of the keys. So if someone has changed to
encrypted backups then that can be attacked to retrieve recovery keys.

A real issue with iOS security (and with any mobile device) is that
users *want* to have ready and unimpeded access. How many people secure
their iOS device with a reasonable strength password? (Mine is >10
characters, upper/lower/number/symbol). A common user defense against
strong password practice is that "it is always in my possession and I'd
no immediately if it was gone."

Another factor is that people *want* some things to not be stored
securely. For example, if you want your mobile device to join "secure"
networks silently as you come and go and download email, etc. whether or
not it is unlocked -- that information must be available when the device
is locked. Once you understand this the making the encryption of
keychain items optional per entry starts to make sense -- but it is
something that, from a security perspective, you need to be aware of.

Apple is good at making devices that people want to use. If they had
created a more secure device (e.g., encryption of keychain items
mandatory with a secure implementation of the encryption) then it would
be less usable and people wouldn't want to use it as much.

Finally, I think it is a mistake to focus on Apple here. Android makes
effectively the same compromises with respect to security for all of the
same reasons. I also think it is a mistake to focus on smart phones and
tablets when people are using laptops that have similar security issues.

Instead, the issue should be more of mobile devices used to store or
process sensitive information and how to best accommodate that. Full
disk encryption is a hindrance to someone performing "dead" forensic
analysis on the device, but generally meaningless in common theft (left
logged on in a hotel lobby) or credential theft (public wireless)
scenarios. Basically, what is being protected and from what attacks.

Tim Doty