portable encrypted CD/USB

I see in the netbsd guide about using the CGD to create an
encrypted CD.
It does note that such a CD can't be read with any other
OS.

Does anyone know of a tool to do something similar that is
cross-OS
between especially NetBSD and Debian GNU/Linux?  Ideally, it
wouldn't be
limited to CD but could be used on e.g. USB sticks.

Thanks,

Doug.

Douglas Allan Tutty:

> Does anyone know of a tool to do something similar that
is cross-OS
> between especially NetBSD and Debian GNU/Linux? 
Ideally, it wouldn't
> be limited to CD but could be used on e.g. USB sticks.


cfs, see Stefan Schumacher's HOWTO at 

http://net-tex.dnsalias.org/~stefan/nt/unix/cfs.html


-- 
Mark Weinem
Jabber: weinemjabber.cz
PGP-Key available

Douglas Allan Tutty wrote:
> I see in the netbsd guide about using the CGD to create
an encrypted CD.
> It does note that such a CD can't be read with any
other OS.
>
> Does anyone know of a tool to do something similar that
is cross-OS
> between especially NetBSD and Debian GNU/Linux? 
Ideally, it wouldn't be
> limited to CD but could be used on e.g. USB sticks.
>
> Thanks,
>
> Doug.
>
>   
Things at a filesystem level are highly incompatible and
specific to the OS,
easier (not as elegant though) would be to script something
around well 
ported tools like openssl

(you might even include scripts for win/lnx & bsd) that
call
openssl enc -aes-256-cbs -d -pass "$1" -in
"$2.cryp" -out "$2"

and this converts an encrypted file.
On unix you can then mount this file as a loopback device
and unlink it 
immediatly.
on windows ( with cygwin tar or similar) you could also use
openssl (or 
any other encrypting tool)


This would be my 5c of have it compatible

How well ported is cfs? Does it still only use des ? ( I
would hihgly 
advise against des (even 3des wouldn't be my choice)

It would be cool if someone develops a device that acts like
a 
hard-drive (flash disk) and if a certain file is written to
it, would 
use this (filename or content) to decrypt the flash and
present the 
decrypted content as an standard folder inside this
"virtual" drive.

Sounds like a pet project....

thilo

Also sprach Thilo Jeremias (jeremiasoptushome.com.au)
> Douglas Allan Tutty wrote:
> >I see in the netbsd guide about using the CGD to
create an encrypted CD.
> >It does note that such a CD can't be read with any
other OS.
> >
> >Does anyone know of a tool to do something similar
that is cross-OS
> >between especially NetBSD and Debian GNU/Linux? 
Ideally, it wouldn't be
> >limited to CD but could be used on e.g. USB
sticks.
> >
> >Thanks,
> >
> >Doug.

  
> How well ported is cfs? Does it still only use des ? (
I would hihgly 
> advise against des (even 3des wouldn't be my choice)

CFS supports 3DES, MacGuffin and Blowfish. I use it since
2001, first
for ~stefan, but since CGD is available I only encrypt some
directories (~/mail, ~/.gnupg and so) which shall be
protected even if
CGD is configured and mounted. 

I keep a Howto for CFS at [1] or [2] and use it still to
protect CDs
and flash sticks. I tested it with some friends on NetBSD,
FreeBSD,
OpenBSD and Gentoo-Linux, so it is currently the most
portable crypto
fs at least in a unix world. 

If one only uses NetBSD, one could use CGD on a container.
Simply
create a file as container with dd, vnconfig it and create a
CGD layer
and a filesystem on. Then write it onto a CD.


[1] 
http://net-tex.dnsalias.org/~stefan/nt/unix/cfs.html
    english Howto on CFS on NetBSD
[2] http://net-tex.dnsalias.org/~stef
an/nt/netbsd/advocacy/guug-uptimes-cgd_cfs.pdf
    German article on CGD and CFS on NetBSD, published in
the UpTimes
	Dec. 2006

-- 
PGP FPR: CF74 D5F2 4871 3E5C FFFE  0130 11F4 C41E B3FB AE33
http://www.net-tex.de   
                             
http://www.cryptomancer.de

-- 
Worum haben die Menschen von Kindesbeinen an gebetet, wovon
haben sie geträumt,
womit haben sie sich gequält? Daß irgendeiner ihnen ein für
allemal sage, was das
Glück ist, und sie mit einer Kette an dieses Glück schmiede.
Und ist dies nicht 
gerade das, was wir tun? Der uralte Traum vom Paradies ...
Jewgenij Iwanowitsch Samjatin, »Wir«

> CFS supports 3DES, MacGuffin and Blowfish. I use it
since 2001, first
> for ~stefan, but since CGD is available I only encrypt
some
> directories (~/mail, ~/.gnupg and so) which shall be
protected even if
> CGD is configured and mounted. 
>
>   
Hm, ?

If I understand CFS correctly it hides/scrambles directory
names from 
non root users, but it provides no protection against root
while the 
directory is open,
why is this then more secure than chmod 600 ?

To MacGuffin: (from wikipedia)
In cryptography, MacGuffin is a block cipher created in 1994
by Bruce 
Schneier and Matt Blaze at a Fast Software Encryption
workshop. It was 
intended as a catalyst for analysis of a new cipher
structure, known as 
Generalized Unbalanced Feistel Networks (GUFNs) —
"MacGuffin" refers to 
a plot device that holds no meaning or purpose of its own
except to 
motivate the characters and advance the story. The
cryptanalysis 
proceeded very quickly, so quickly that the cipher was
broken at the 
same workshop by Vincent Rijmen and Bart Preneel.

http://en.wik
ipedia.org/wiki/MacGuffin_(cipher)

thilo

Also sprach Thilo Jeremias (jeremiasoptushome.com.au)
 
> >CFS supports 3DES, MacGuffin and Blowfish. I use it
since 2001, first
> >for ~stefan, but since CGD is available I only
encrypt some
> >directories (~/mail, ~/.gnupg and so) which shall
be protected even if
> >CGD is configured and mounted. 
> >
> >  
> Hm, ?
> 
> If I understand CFS correctly it hides/scrambles
directory names from 
> non root users, but it provides no protection against
root while the 
> directory is open,
> why is this then more secure than chmod 600 ?

So what? You cannot protect against root with any kind of
encrypted
filesystem, be it CFS, CGD or whatever. If you cannot trust
root,
don't use that machine. 

-- 
PGP FPR: CF74 D5F2 4871 3E5C FFFE  0130 11F4 C41E B3FB AE33
http://www.net-tex.de   
                             
http://www.cryptomancer.de

-- 
Worum haben die Menschen von Kindesbeinen an gebetet, wovon
haben sie geträumt,
womit haben sie sich gequält? Daß irgendeiner ihnen ein für
allemal sage, was das
Glück ist, und sie mit einer Kette an dieses Glück schmiede.
Und ist dies nicht 
gerade das, was wir tun? Der uralte Traum vom Paradies ...
Jewgenij Iwanowitsch Samjatin, »Wir«

> So what? You cannot protect against root with any kind
of encrypted
> filesystem, be it CFS, CGD or whatever. If you cannot
trust root,
> don't use that machine. 
>
>   
Very true!

I was really just wondering, if you have CGD, what is the
advantage to 
also use CFS for mail?

thilo

Also sprach Thilo Jeremias (jeremiasoptushome.com.au)
> 
> >So what? You cannot protect against root with any
kind of encrypted
> >filesystem, be it CFS, CGD or whatever. If you
cannot trust root,
> >don't use that machine. 
> >
> >  
> Very true!
> 
> I was really just wondering, if you have CGD, what is
the advantage to 
> also use CFS for mail?

CFS and CGD have a different model. I only use my Laptop to
work at
and store all my data on /home. If I need to access that
data, eg. a
CVS directory for a customer or slides for a presentation at
a
Conference, I have to mount /home. Therefor, I have to
config the CGD
device. At that moment, all files on /home are unprotected.


CFS works on the normal file system layer, so I use it to
protect
sensitive data, like my mailbox or PGP-Keys. I can cgdconfig
and mount
my home to access my not-that-sensitive data, but still keep
my very
sensitive data protected by CFS. 

Even if someone hacks into my laptop while being at a
conference,
sensitive data is still encrypted with cfs. 
That's why I combine both models. 



Hope that helps,
Stefan
-- 
PGP FPR: CF74 D5F2 4871 3E5C FFFE  0130 11F4 C41E B3FB AE33
http://www.net-tex.de   
                             
http://www.cryptomancer.de

-- 
Worum haben die Menschen von Kindesbeinen an gebetet, wovon
haben sie geträumt,
womit haben sie sich gequält? Daß irgendeiner ihnen ein für
allemal sage, was das
Glück ist, und sie mit einer Kette an dieses Glück schmiede.
Und ist dies nicht 
gerade das, was wir tun? Der uralte Traum vom Paradies ...
Jewgenij Iwanowitsch Samjatin, »Wir«

Thilo Jeremias <jeremiasoptushome.com.au>
writes:

> If I understand CFS correctly it hides/scrambles
directory names from
> non root users, but it provides no protection against
root while the
> directory is open,
> why is this then more secure than chmod 600 ?

1) The backup media will have ciphertext, not plaintext.

2) The ciphertext may be on a fileserver (NFS, coda, etc.)
that is under
   the control of someone else.

3) Needing the key means that an attacker has to trojan
something, or be
   there at the right time.  This isn't really comforting,
but it's
   better than nothing.
 

On Tue, 15 May 2007 22:55:05 +1000
Thilo Jeremias <jeremiasoptushome.com.au>
wrote:

> 
> > CFS supports 3DES, MacGuffin and Blowfish. I use
it since 2001,
> > first for ~stefan, but since CGD is available I
only encrypt some
> > directories (~/mail, ~/.gnupg and so) which shall
be protected even
> > if CGD is configured and mounted. >
> >   Hm, ?
> 
> If I understand CFS correctly it hides/scrambles
directory names from
> non root users, but it provides no protection against
root while the
> directory is open, why is this then more secure than
chmod 600 ?

Correct.  Encrypted disks are useful against enemies with
physical
access, not login access.  The intent was to protect backup
tapes and
NFS repositories.



		--Steve Bellovin, http://www.cs.columbi
a.edu/~smb