On Mon, Dec 23, 2013 at 4:18 PM, Alex Pilon <alp [ at ] alexpilon [ dot ] ca> wrote: > On Mon, Dec 23, 2013 at 03:47:05PM -0500, Robert P. J. Day wrote: > > LUKS does block device symmetric encryption. It's in a way a wrapper > around dm-crypt. Plain dm-crypt requires you to specify all the > parameters manually, whereas LUKS creates a header at the beginning of > the block device. dm-crypt requires you to understand the crypto, and > won't do things like salting your secret. LUKS will randomly generate > (and salt if I recall correctly) a master secret, and provide ten > “slots” for weaker secrets (e.g., passwords, passphrases, or binary data > of your chosing), which it'll run through PBKDF2. This is close, but there is no "weaker" secret. For each "slot" (of which I think there are 8) that is activated, the "Master" key is encrypted using the passphrase/data that is provided when the slot is enabled/configured (when you create a new LUKS device, there is only a single slot activated). In the default configuration, the Master Key is an AES encryption key. Later, when you're prompted for the passphrase to unlock the LUKS device, cryptsetup loops through each enabled slot using the provided passphrase and gets some Master Key as a result. It verifies (I can't remember how...looks for a header?) if this Master Key makes sense i.e., it successfully decrypts some data in a way that yields correct plaintext. So, with multiple slots enabled the Master Key is encrypted multiple times using different passphrases and PBKDF2. mh -- Martin Hicks P.Eng. | mort [ at ] bork [ dot ] org Bork Consulting Inc. | +1 (613) 266-2296