[dm-crypt] Crypting a filesystem using an asymmetric GPG key ?

[dm-crypt] Crypting a filesystem using an asymmetric GPG key ?

[Il Sdrucciole]

[-- Attachment #1: Type: text/plain, Size: 570 bytes --]

Hello everybody,

I am currently using several GNU/Linux distros (Ubuntu, Gentoo) and I would
like to crypt my entire disk.

But the point is, I do not want to use any symmetric algorithm. More, I have
got GPG keys: why not use them to encrypt my FS ? By doing this, I would
have to give my private key and passphrase at boot time, and security would
be improved (possibility to use smartcards, etc.).

So my question is, *Is there a way to crypt a filesystem with a GPG
asymmetric key ?*

Linking the standards would be very user-friendly.

Thanks alot,
Il Sdrucciole.

[-- Attachment #2: Type: text/html, Size: 615 bytes --]

Re: [dm-crypt] Crypting a filesystem using an asymmetric GPG key ?

[Christoph Anton Mitterer]

Hi.

OpenPGP also uses symmetric encryption (at least for the actual data).

What you can do is: Encrypt the dm-crypt/LUKS key with OpenPGP, which  
is what I do personally.

If you're using Debian or a derivate, I can copy you a sophisticated  
keyscript for Debian's cryptsetup packge, which does this job.
The one included with Debian, doesn't work and/or as several  
functionallity/security problems (not sure about the last status, as I  
didn't follow it anymore).


Cheers,
Chris.

Re: [dm-crypt] Crypting a filesystem using an asymmetric GPG key ?

[Arno Wagner]

On Sat, Mar 12, 2011 at 05:43:15PM +0000, Il Sdrucciole wrote:
> Hello everybody,
> 
> I am currently using several GNU/Linux distros (Ubuntu, Gentoo) and I would
> like to crypt my entire disk.
> 
> But the point is, I do not want to use any symmetric algorithm. 

There weill not be a way around that, unless you 
a) write it yourself and
b) are willing to take a massive performance hit, as in a factor
   1000 slower than symmetrical. Expect something like
   100kB/s for RSA1024 and something like 25kB/s for RSA2048.
   (Writing will be faster though.) That is floppy speed.

> More, I have
> got GPG keys: why not use them to encrypt my FS ? By doing this, I would
> have to give my private key and passphrase at boot time, and security would
> be improved (possibility to use smartcards, etc.).

Aeh, no? LUKS is about as secure as GPG is, likely more, as GPG has
no anti-forensics. And you can already use a GPG key with plain 
dm-crypt to protect the master key.
 
> So my question is, *Is there a way to crypt a filesystem with a GPG
> asymmetric key ?*

Yes, but you do not want to do that, see above.
 
> Linking the standards would be very user-friendly.

What standards?

Arno
-- 
Arno Wagner, Dr. sc. techn., Dipl. Inform., CISSP -- Email: arno@wagner.name 
GnuPG:  ID: 1E25338F  FP: 0C30 5782 9D93 F785 E79C  0296 797F 6B50 1E25 338F
----
Cuddly UI's are the manifestation of wishful thinking. -- Dylan Evans

If it's in the news, don't worry about it.  The very definition of 
"news" is "something that hardly ever happens." -- Bruce Schneier 

Re: [dm-crypt] Crypting a filesystem using an asymmetric GPG key ?

[Il Sdrucciole]

[-- Attachment #1: Type: text/plain, Size: 2208 bytes --]

Thank you both for your replies, I understand now why RSA is never used for
disk encryption.
What you say in b) is never explicated in the lots of
documentation/tutorials I gathered on the web. I'm wondering now if it's not
better to directly spot the research papers...
Anyway your answer enlightened me alot about the reason for not using
asymmetric algorithms here.

Cheers,
Sdrucciole.

2011/3/13 Arno Wagner <arno@wagner.name>

> On Sat, Mar 12, 2011 at 05:43:15PM +0000, Il Sdrucciole wrote:
> > Hello everybody,
> >
> > I am currently using several GNU/Linux distros (Ubuntu, Gentoo) and I
> would
> > like to crypt my entire disk.
> >
> > But the point is, I do not want to use any symmetric algorithm.
>
> There weill not be a way around that, unless you
> a) write it yourself and
> b) are willing to take a massive performance hit, as in a factor
>   1000 slower than symmetrical. Expect something like
>   100kB/s for RSA1024 and something like 25kB/s for RSA2048.
>   (Writing will be faster though.) That is floppy speed.
>
> > More, I have
> > got GPG keys: why not use them to encrypt my FS ? By doing this, I would
> > have to give my private key and passphrase at boot time, and security
> would
> > be improved (possibility to use smartcards, etc.).
>
> Aeh, no? LUKS is about as secure as GPG is, likely more, as GPG has
> no anti-forensics. And you can already use a GPG key with plain
> dm-crypt to protect the master key.
>
> > So my question is, *Is there a way to crypt a filesystem with a GPG
> > asymmetric key ?*
>
> Yes, but you do not want to do that, see above.
>
> > Linking the standards would be very user-friendly.
>
> What standards?
>
> Arno
> --
> Arno Wagner, Dr. sc. techn., Dipl. Inform., CISSP -- Email:
> arno@wagner.name
> GnuPG:  ID: 1E25338F  FP: 0C30 5782 9D93 F785 E79C  0296 797F 6B50 1E25
> 338F
> ----
> Cuddly UI's are the manifestation of wishful thinking. -- Dylan Evans
>
> If it's in the news, don't worry about it.  The very definition of
> "news" is "something that hardly ever happens." -- Bruce Schneier
> _______________________________________________
> dm-crypt mailing list
> dm-crypt@saout.de
> http://www.saout.de/mailman/listinfo/dm-crypt
>

[-- Attachment #2: Type: text/html, Size: 3021 bytes --]

Re: [dm-crypt] Crypting a filesystem using an asymmetric GPG key ?

[Arno Wagner]

On Sun, Mar 13, 2011 at 07:22:12AM +0000, Il Sdrucciole wrote:
> Thank you both for your replies, I understand now why RSA is never used for
> disk encryption.
> What you say in b) is never explicated in the lots of
> documentation/tutorials I gathered on the web. I'm wondering now if it's not
> better to directly spot the research papers...
> Anyway your answer enlightened me alot about the reason for not using
> asymmetric algorithms here.
> 
> Cheers,
> Sdrucciole.


You are welcome. There is indeed still mostly half-right and
sometimes plain wrong information about crtyptography on the
web. Too many people think they have understood what it is about
while they have clearly not. 

For a good overview, I would recommend Schneier's "Cryptography 
Engineering". Research papers in the area tend to be pretty
hard to read nowadays.

Arno



 
> 2011/3/13 Arno Wagner <arno@wagner.name>
> 
> > On Sat, Mar 12, 2011 at 05:43:15PM +0000, Il Sdrucciole wrote:
> > > Hello everybody,
> > >
> > > I am currently using several GNU/Linux distros (Ubuntu, Gentoo) and I
> > would
> > > like to crypt my entire disk.
> > >
> > > But the point is, I do not want to use any symmetric algorithm.
> >
> > There weill not be a way around that, unless you
> > a) write it yourself and
> > b) are willing to take a massive performance hit, as in a factor
> >   1000 slower than symmetrical. Expect something like
> >   100kB/s for RSA1024 and something like 25kB/s for RSA2048.
> >   (Writing will be faster though.) That is floppy speed.
> >
> > > More, I have
> > > got GPG keys: why not use them to encrypt my FS ? By doing this, I would
> > > have to give my private key and passphrase at boot time, and security
> > would
> > > be improved (possibility to use smartcards, etc.).
> >
> > Aeh, no? LUKS is about as secure as GPG is, likely more, as GPG has
> > no anti-forensics. And you can already use a GPG key with plain
> > dm-crypt to protect the master key.
> >
> > > So my question is, *Is there a way to crypt a filesystem with a GPG
> > > asymmetric key ?*
> >
> > Yes, but you do not want to do that, see above.
> >
> > > Linking the standards would be very user-friendly.
> >
> > What standards?
> >
> > Arno
> > --
> > Arno Wagner, Dr. sc. techn., Dipl. Inform., CISSP -- Email:
> > arno@wagner.name
> > GnuPG:  ID: 1E25338F  FP: 0C30 5782 9D93 F785 E79C  0296 797F 6B50 1E25
> > 338F
> > ----
> > Cuddly UI's are the manifestation of wishful thinking. -- Dylan Evans
> >
> > If it's in the news, don't worry about it.  The very definition of
> > "news" is "something that hardly ever happens." -- Bruce Schneier
> > _______________________________________________
> > dm-crypt mailing list
> > dm-crypt@saout.de
> > http://www.saout.de/mailman/listinfo/dm-crypt
> >

> _______________________________________________
> dm-crypt mailing list
> dm-crypt@saout.de
> http://www.saout.de/mailman/listinfo/dm-crypt


-- 
Arno Wagner, Dr. sc. techn., Dipl. Inform., CISSP -- Email: arno@wagner.name 
GnuPG:  ID: 1E25338F  FP: 0C30 5782 9D93 F785 E79C  0296 797F 6B50 1E25 338F
----
Cuddly UI's are the manifestation of wishful thinking. -- Dylan Evans

If it's in the news, don't worry about it.  The very definition of 
"news" is "something that hardly ever happens." -- Bruce Schneier