> From: David Lang [mailto:[email protected]] > > In any case, does it really make a difference if the encryption key is the > password stretched or just stored and 'unlocked' in some way by the > password? > > As long as there is a way to tell if it was the right passowrd or not, all the > attacker needs to do is to attack the password space. they don't have to > attack > the stronger key space.
>From a vulnerability standpoint, you're right. No, it doesn't matter if the >cipher key is produced by the key derivation process directly, or if the key >derivation process is used to unlock a stored cipher key. Once you've >completed the key derivation process, it's only one more step to unlock a >stored cipher key. In either case, assuming the password strength is >significantly less than the strength of a random cipher key, the obvious weak >point to attack is the password itself, and not the cipher key. The reason for using this technique of key derivation process to unlock the cipher key is logistical. By doing this, you create the ability to easily change the password for the volume, without needing to re-encrypt the whole volume. But it's important to be aware, that if an attacker knows your old password *and* has a copy of your old header, then security is compromised, and you really need to re-encrypt the whole volume. On the flip side, this characteristic is precisely what makes truecrypt a viable option for me to deploy to users at work. I first encrypt the volume using a password that I know. I make a backup of the header. (Simply create rescue media, which is a built-in feature.) I then give the system to the user, and ask them to set a new password. We both keep our passwords secret, but if they're ever unavailable for some reason (or they forget their password) I can still recover the volume using my rescue media and the old password. _______________________________________________ Tech mailing list [email protected] https://lists.lopsa.org/cgi-bin/mailman/listinfo/tech This list provided by the League of Professional System Administrators http://lopsa.org/
