-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On 07/14/2011 03:35 PM, Arno Wagner wrote: > On Thu, Jul 14, 2011 at 01:55:50PM +0200, Ma Begaj wrote: >>> Also note that an attacker that has access to the storage could >>> patch your GnuPG binary or other system components. >> >> well that is an another story because an attacker could in that >> case patch cryptsetup too. if s/he can do that it is not important >> whether you use encrypted key file on usb stick or directly >> cryptsetup. > > Indeed. But are there any realistic scenarios where > > a) a passphrase is signifiacntly less secure than an encrypted > passphrase stored on USB with a second pasphrase to decrypt that > > and > > b) the attacker does not have the possibility to patch > GnuPG/cryptup/other things that make the second passphrase just as > weak as the first one? > > My claim is that a realistic risk analysis will show there are no > such scenarios that are typical and hence having an encrypted > passphrase on an USB stick does not offer improved security. Improved security over which other setup? a) Unencrypted passphrase stored on a USB key. Here the second encryption step will probably give additional security in case the user looses the USB key. b) Directly entering passphrase without the need of a USB key. Here we have a typical risk of users using the same passphrase for different things or even of writing it down (on a post-it note on the screen or keyboard...). If we depend upon a USB stick with the real passphrase (encrypted by the one on the post-it note) being present at boot the attacker won't be able to utilize that passphrase. If we move kernel+initrd+cryptsetup to the USB stick and boot the machine from USB, we can even encrypt the entire harddisk, thus even someone with physical access to the machine cannot patch cryptsetup/gnupg. Now it only boils down to whether a user writing down his passphrase will remember to remove the USB key ;) Regards, Heiko P.S: Thinking of law enforcement as the attacker (guess that is not that a great risk for most of us), it is possible to destroy all access to your data by destroying all the USB keys with the encrypted passphrase on them - and then you can even tell them your passphrase... - -- eMails verschlüsseln mit PGP - privacy is your right! Mein PGP-Key zur Verifizierung: http://pgp.mit.edu -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.17 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ iEYEARECAAYFAk4e+V0ACgkQ/Vb5NagElAW5aQCfVU4p9/H64K+AQjgl33qSJjQJ 4BEAnRQ9tRptBRHM8JDdFOigyHjPH58N =utnI -----END PGP SIGNATURE----- _______________________________________________ dm-crypt mailing list dm-crypt@xxxxxxxx http://www.saout.de/mailman/listinfo/dm-crypt
