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Re: [Issue 4145] Master passphrase and encrypted credentials cache

From: Greg Stein <gstein_at_gmail.com>
Date: Tue, 27 Mar 2012 11:56:08 -0400

On Mar 27, 2012 12:55 AM, "Daniel Shahaf" <d.s_at_daniel.shahaf.name> wrote:
>...
> > On 27.03.2012 05:23, Greg Stein wrote:
> > >...
> > > While discussing this on IRC some, I did think of one case where you
> > > want to know they got the correct master passphrase: when they are
> > > updating a server's password. A mis-entry could completely garble the
> > > stored/encrypted contents.
>
> Don't ew have some other ways of addresing that use-case? Such as, say,
> encrypting a random string, and at decrypting compare the decrypted
> text's sha1 to the value computed at encryption time?

There ya go. I knew we could tease out a solution. That sounds good to me.

So, for each password, we store two more 16-byte blocks of encrypted data,
and a SHA1 has (20 bytes). At decrypt time, we also decrypt those blocks,
hash the 32 byte result, and compare against the hash.

I would also suggest that we append those two blocks to the padded
password, so they get the advantage of CBC, without needing to pick a
second IV.

Cheers,
-g
Received on 2012-03-27 17:56:40 CEST

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