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Date: Fri, 11 Jan 2013 00:06:39 +0200
From: Milen Rangelov <>
Subject: Re: npdf2john


I was contacted by LastPass regarding that offline attack. To cut the long
story short, they were open and friendly and offered me to help with the
cryptography questions I had. They did not believe we do an offline attack
initially (they thought it was captured network traffic) so I explained
what we did. They also told me what is being employed in Windows (the
mysterious encrypted IE and Firefox stuff). So bad news, we're up to
something evil - DPAPI.

What really struck me as odd is that the encrypted xml on Android looks
very much like the sxml from Windows and I doubt that there is DPAPI
implementation for Java on Android. But then I am a noob in the Android
world, so who knows :)

So basically we have a real problem with that. DPAPI was reverse-engineered
and I need to read the paper, but from what I remember it is tied to the
local account's password in a way (a SHA1 hash of the password is applied
somehow from what I remember). So in the windows case, we would need the
local account password which makes it really hard to crack :(

If anyone is acquainted with how DPAPI works, details would be much
appreciated :)

On Thu, Jan 10, 2013 at 6:09 PM, shane Shane

> > Well unfortunately the mail address takes part into the key derivation
> process
> By default the last pass app remembers the email address so for most
> offline attacks this shouldn't be an issue. Also chances are the
> individuals phone has an email address or two on it that is most likely the
> email address used for their last pass account so even if the user has
> unchecked remember my email in the app you'd still have a good guess at the
> person's last pass email.
> Regards,
> Shane

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