Re: Deniable data storage

[John Kelsey]

At 06:58 PM 11/5/03 -0800, James A. Donald wrote:
I want to store information deniably.
..
This would contain various items of information that one could
extract by supplyin a secret, symmetric, key.   A random key would
extract a block of gibberish of random length   There would be no
indication as to how many bits of meaningful data were stored in the
block, though obviously they would have to add up to less than the
size of the block.
I believe one of Ross Anderson's students did something like this a few 
years ago, basically using error-correcting codes with a lot of 
redundancy.  The basic idea is that you use some kind of massive error 
correction and use a different sequence of bits with each key, so that 
you're very unlikely to have enough of your message bits clobbered by 
another message to make it impossible to decode correctly.  (It seems like 
there'd be a problem with information leakage about number of channels 
here, if you had a message encoded in that block of bits, because you would 
know when you decoded it how often you'd had bits flipped, but maybe they 
resolved that somehow.)

--John Kelsey, [EMAIL PROTECTED]
PGP: FA48 3237 9AD5 30AC EEDD  BBC8 2A80 6948 4CAA F259

Political Hyprocrisy in action.

[Neil Johnson]

I'm surprised no one has commented on Al Gore's speech 
(http://www.moveon.org/gore/speech2.html) where he talks about all the evil 
things that the Bush administration has done to  to undermine our civil 
liberties.

Got two words for ya Al:  Clipper Chip

-- 
Neil Johnson
http://www.njohnsn.com
PGP key available on request.

Re: [Mac_crypto] MacOS X (Panther) FileVault

[R. A. Hettinga]

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Subject: Re: [Mac_crypto] MacOS X (Panther) FileVault
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Date: Thu, 13 Nov 2003 13:15:03 +

On 13 Nov 2003, at 5:12, David Shayer wrote:

 I was told that FileVault replaces your home directory with an
 encrypted disk image, much like PGP Disk, so its probably blockwise
 underneath the file system layer. Files in your home directory are
 copied into the disk image, and some file system links redirect calls
 to the home directory to the disk image, and keep the user from seeing
 it as another mounted disk.

This is basically correct.  FileVault uses an auto-mounting version of
the encrypted disk image facility that was in 10.2, tweaked to allow
the image to be opened even before your main key chain is available
(since the key chain is stored inside your home directory).  The
standard encrypted image format uses a random key stored on your key
chain, which is itself encrypted with a salted and hashed copy of the
keychain pass phrase, which defaults to your login password.  My
suspicion is that for the FileVault there is some other key chain file
in the system folder which stores the key for decrypting your home
directory disk image and that the pass phrase for that is just your
login password.

 File Vault will automatically expand or contract the disk image at
 certain points. It creates a new image, copies everything over, and
 deletes the old image.

Yup, it essentially does an hdiutil compact command when you log out.

 I don't know what mode of AES-128 it uses.

I believe that it uses counter mode, since it's efficient when doing
random access to the encrypted data.

Nicko

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-- 
-
R. A. Hettinga mailto: [EMAIL PROTECTED]
The Internet Bearer Underwriting Corporation http://www.ibuc.com/
44 Farquhar Street, Boston, MA 02131 USA
... however it may deserve respect for its usefulness and antiquity,
[predicting the end of the world] has not been found agreeable to
experience. -- Edward Gibbon, 'Decline and Fall of the Roman Empire'

Jews Go Nuclear

[Eric Cordian]

So much for non-proliferation of weapons of mass destruction, right?

http://observer.guardian.co.uk/international/story/0,6903,10613

-

Israel deploys nuclear arms in submarines
Peter Beaumont in London and Conal Urquhart in Jerusalem
Sunday October 12, 2003
The Observer

Israeli and American officials have admitted collaborating to deploy
US-supplied Harpoon cruise missiles armed with nuclear warheads in
Israel's fleet of Dolphin-class submarines, giving the Middle East's only
nuclear power the ability to strike at any of its Arab neighbours.

..

-- 
Eric Michael Cordian 0+
O:.T:.O:. Mathematical Munitions Division
Do What Thou Wilt Shall Be The Whole Of The Law