Aremed with only basic crypto knowledge, I'm trying to understand the security benefits of LUKS over plain-mode dm-crypt. Hopefully this is a good place to ask.
Given the LUKS header contains information describing how the payload is encrypted, would it not be more secure to use plain dm-crypt instead?
I'm thinking that a plain device will just look like random data and won't have a label attached that tells all that it's encrypted data and what the cipher and other details are. Plain mode allows plausible deniability where as LUKS doesn't.
The LUKS header not only contains the master key (albeit it stretched and encrypted) but it also contains up to eight attack vectors that can be used to get the master key. Yet, underlying all this, the same dm-crypt engine is used to encrypt both the plain and luks payloads.
Therefore, attacking a plain or luks payload could be done directly (however impractical that may be), but LUKS throws in some additional ways to crack the data whereas plain-mode gives nothing away.
I guess it may boil down to the fact that a user of plain mode will need to have the actual key and may not store it securely or use a pass-phrase that is only hashed simplistically, whereas a user of LUKS mode will never have the actual key but will use a pass-phrase that is put through a salted iterative key derivation function.
So, is LUKS less secure than plain dm-crypt ?