key security

Leigh S. Jones
Wed Apr 10 01:54:02 2002

The only real security for your encrypted data depends
on the quality of your passphrase, although to some
degree there may be some degree of physical security
that you can provide for your computer.  Computers at
a company are rarely secure, even when locked behind
doors.  If prying eyes really want to see your data,
they can get behind the doors and beyond the boot ROM
password, your computer can be booted from a floppy
or tape giving the invader root access to your whole
drive without even guessing a password.  Or your hard
drive can be unplugged and jumpered over to a laptop
that will soak up everything.  The whole job will be
over quickly and quietly without you ever knowing
anything happened.

You have, basically, 1 defense.  Forget removable
media for the secret key ring file, it will eventually
become such a nuisance to use that you give up on
securely storing it on a regular basis, or else your
secure storage will be insecure.  Unless you do nothing
that anyone would ever be interested in knowing about,
your highly secure password is your only defense.

Frankly, in the present electronic age this is quickly
becoming very important in many more ways than one might
at first imagine.  People don't have to do anything
spicy in their lives to have a very real need to keep
secrets.  Consider the credit card number.

In my business we do nothing that needs to be kept a
secret beyond the occasional intellectual property.  But
we will be using electronic signatures to replace
signatures on paper documents widely very soon, and in
an environment where secret keyrings must be widely
shared.  Password integrity becomes the only available
means for assurance that the system will work.

There's no sense in attempting password security that
exceeds the basic security of the underlying encryption
system.  For the most secure applications it should take
an attacker just a little bit less effort to break GPG's
underlying symmetric-key cryptography than to break your
own password by guessing.  There are ways to assure that
you've selected a password this random while still
making it possible for you to remember your password.
Research them, and but keep the method you use secret.
Don't recommend a method that you like on a public forum
like this one.  If you come on here and tell everyone you
used "head -c 16 /dev/random | mimencode" then
everyone knows how best to attack you.  Better to tell
them you used "head -c 24 /dev/random | mimencode" but
actually use the telephone number for your dead
grandmother that you remember from your youth plus your
dog's name plus two different negative descriptors you use
for your two ex-wives plus your favorite flavor...

----- Original Message -----
From: "Jeroen Valcke" <>
To: <>
Sent: Tuesday, April 09, 2002 12:37 PM
Subject: key security

> Hello,
> I'm new to the list and GnuPG. I have some small (newbie) questions.
> 1/ What about key security. Do you people all leave your private key
> the harddisk of your machine. On Debian linux that's in the .gnupg
> directory. How about putting this whole directory on removable media
> (for example diskette) A colleague of mine has his on a remove USB
> media. Good idea? reactions? impractical?
> 2/ To encrypt a message all I need is the recipients public key,
> Encryption is done solely with the public key of the recipient. My
> private key is not used, is this correct?
> -Jeroen-
> A confused newbie.
> --
> Jeroen Valcke     
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