When I read the manpage for
cryptsetup on Linux about "Plain mode" it says:
Plain dm-crypt encrypts the device sector-by-sector with a single, non-salted hash of the passphrase.
-c option says:
--cipher, -c <cipher-spec> Set the cipher specification string. cryptsetup --help shows the compiled-in defaults. The current default in the distrib‐ uted sources is "aes-cbc-essiv:sha256" for both plain dm-crypt and LUKS.
aes-cbc-essiv:sha256 mean that for each sector of my harddrive a sha256 hash of the passphrase is also stored in the sector?
If that is the case: What is the purpose of storing the hashed passphrase so many times?