Re: Product request - Enterprise whole disk encryption for laptops

[Roger Safian <r-safian () NORTHWESTERN EDU>]

At 04:09 PM 7/15/2006, Valdis Kletnieks put fingers to keyboard and wrote:
> Using a set of 100,000 PCs, distributed.net broke a DES key in some 22 hours.
> That key had (presumably) 56 bits of entropy.  UPPER-lower 0-9 is a total
> of 62 possibilities, call that 64 and we have a *potential* 6 bits of
> entropy per character.  English text/words has about 2.2 (for short phrases,
> probably closer to 3).  So 16 characters will vary from 48 bits to 96 bits
> of entropy, depending how random they are. 'SleepyFuzzyABC12' probably only
> has 48 or so, 'WM6PoJF7fzVWXcO5' closer to 96.
>
> 48 bits of entropy will break 2**(56-48) or 256 times faster than the
> distributed.net challenge - so rent a botnet of 100K PCs for 10 minutes,
> or a net of 500 bots for a day, and you have the key.
>
> 96 bits of entropy will break 2**(96-56) or 109,9511,627,776 times slower
> than the DES key - or Not A Worry at current technology.  Whether your users
> will let you force them to use that sort of password is another question :)

A couple of comments.

To date I have heard of NO bad guys using, say a botnet, to crack passwords.
That's not to say it's not happening, just that it's not being reported.  Further,
since nodes in a botnet come and go, it may not be an ideal way to distribute
the brute force attempt.  I can't think of any other obvious way for the
bad guys to gain access to 100,000 computers.  I guess they could trojan
SETI at home, but something tells me that would only work for a short period
of time.  My personal opinion is it's just not worth their trouble.  Sell
it on eBay and be done with it.  Now, real espionage is a different story,
but as I've already said there are better methods of gaining access to the
key in those opportunities.  My conclusion is that a reasonable passphrase
protecting an encrypted drive is likely to defend itself very well in
a non-targeted theft.

Now as for getting people to use a stronger passphrase, I think the key
there is the way we sell it to them.  First, I think you can make a stronger
argument to a individual who has sensitive data on the machine and has
legitimate need for it.  No how do you do this.  I think we need to
move away from complicated in favor of length.  I guess what I am saying
is that I expect I would have more trouble with my community of I tried
to sell them on the value of using a passphrase such as WM6PoJF7fzVWXcO5.
It's just to difficult for them to remember, and that's going to eventually
sink the program.  Rather get them to use something like "1 am not going to
PAY a lot for the muffler!".  It's easy to remember, it's much longer, and
therefore much stronger, and it has a reasonable character set combination.
My conclusion is that having a successful encryption program for sensitive
data really all depends on one thing.  How successful you can be working
with your community to make sure they understand why this is important.

Anyway - I'm working on this right now.  I'd like to have a real policy
in a couple of months or so.  When I do, I will share it.  Thanks to
everyone for your participation in this discussion.


--
Roger A. Safian
r-safian () northwestern edu (email) public key available on many key servers.
(847) 491-4058   (voice)
(847) 467-6500   (Fax) "You're never too old to have a great childhood!"