[Dovecot] E-Mail Encryption

[Frank Leonhardt]

On 19/07/2009 16:03, Tapani Tarvainen wrote:
> On Sun, Jul 19, 2009 at 03:48:25PM +0100, Frank Leonhardt
(t200907 at fjl.co.uk) wrote:
> 
>> Encrypting the whole disk is good if the server gets pinched. My servers
are
>> behind several layers of hi-tech locks with permanent security guards on
the
>> door. I'm not too worried about them.
> 
> How much good do your locks do when police comes and wants to
> confiscate your servers because they suspect one of your users
> has done something criminal? Do you trust they take as good care
> of the machines as you do?

How do you know I'm *not* the Police?

We're in very interesting territory here, and it's going to depend on your
local laws. In England the police are pretty okay about things, and are glad
to have you extract the data yourself. If they really want to do it
themselves it's easy enough to give them half a mirror.

>> I'm not in favour of whole disk encryption for data recovery and forensic
>> reasons.
> 
> Some people favour it for the very same reasons...

Again, it depends on the jurisdiction. In England, if you can't decrypt the
data it can be a bit awkward (RIPA) - unless it's clearly NOT your data in
the first place (i.e. a message body).

>> Protection against a rogue admin by encryption is a red herring. Such a
>> person would simply not enable the encryption in the first place.
> 
> Here I beg to differ. You are right in the simple situation where
> there's just one admin who's a crook to begin with, but often enough
> there're several and only one (or few) unreliable ones among them,
> and even if they're all good they can be forced by their bosses
> or blackmailers or even untrustworthy authorities.
> This is not purely theoretical, I can assure you.

Yes, but the rogue administrator ought to be able to circumvent encryption
anyway - if it's whole disk it's effectively not encrypted. It'd rely on a
policy of someone else periodically checking the files to see if they were
still encrypted - don't see that happening somehow! And even then, an
administrator could easily tee the data off before its stored.

The main reason I'd be in favour of application-based file encryption is to
get around the fact that whole-disk encryption is meaningless as protection
from the operator - if the operator is dodgy (or someone's bypassed
security) then they can read the mail files just as easily as everything
else. If the files themselves are encrypted then access to the running
system won't reveal their contents (although it would help).