On Wed, 31 Mar 2010, Matthew Dillon wrote:
and block ciphers, is that you need a significant amount of random salt in each randomly accessible unit to protect against various forms of attack.
Against dictionary attacks, as I understand it. The salt ensures that you can't just pre-generate a list of hashes once, from a huge dictionary, but have to attack each system separately.
The salt must still be available to the system for it to be able to decrypt things, which as far as I can see means outside the encrypted volume and readable by root -- and any attacker that can gain physical access. (If it's not available to the system, it's not a salt, but something else, like part of the password.)
The salt can be applied as part of the encoding/decoding stream (it doesn't have to be all up-front), but the question is where does one store that salt?
/etc/cgd/<device>. :-) (not world readable) MAgnus
