Hi John, the cryptsetup man-page has additional information about the different ways a passphrase can be passed to it and what the conventions are in section "NOTES ON PASSPHRASE PROCESSING FOR PLAIN MODE". That should get you started. If you want to generate a key that is the same as generated by a specific passphrase, the easiest way is probably to map the container with the passphrase and then extract the key from dm-crypt. I am not sure this works, but if it does, FAQ Item 6.10 has the information. dm-crypt just gets a cipher and a key and does not know whether that key is a LUKS master key or a plain key. Your example may fail because of differences in padding, for example. Also note that sha512sum <<< 'my_passphrase' | head -c 128 > mykey produces an ASCII representation of the hash truncated to 128 characters, while you probably want a binary representation that is 128 bit long. Arno On Fri, Nov 07, 2014 at 17:34:39 CET, John Lane wrote: > I'm trying to use plain dm-crypt. I have an example like this > > $ cryptsetup open /dev/sda mydisk --type plain --hash sha512 > > that works fine. I enter 'password' as the pass phrase when requested. > > I want to create an equivalent key-file so that I can do > > $ cryptsetup open /dev/sda mydisk --type plain --key-file mykey > > I couldn't find a cryptsetup command do to this, so I tried these: > > $ openssl dgst -sha512 -binary <<< 'password' > mykey > also > $ sha512sum <<< 'my_passphrase' | head -c 128 > mykey > > without success. > > As I understand it, the key file contains a binary key that is used > as-is, so I would have thought the first try above would have worked. I > even used xxd to check that mykey contained the hash in binary data. > > How can I make a key-file that is equivalent to a keyed-in passphrase? > > Thanks in advance. > > _______________________________________________ > dm-crypt mailing list > dm-crypt@xxxxxxxx > http://www.saout.de/mailman/listinfo/dm-crypt -- Arno Wagner, Dr. sc. techn., Dipl. Inform., Email: arno@xxxxxxxxxxx GnuPG: ID: CB5D9718 FP: 12D6 C03B 1B30 33BB 13CF B774 E35C 5FA1 CB5D 9718 ---- A good decision is based on knowledge and not on numbers. -- Plato If it's in the news, don't worry about it. The very definition of "news" is "something that hardly ever happens." -- Bruce Schneier _______________________________________________ dm-crypt mailing list dm-crypt@xxxxxxxx http://www.saout.de/mailman/listinfo/dm-crypt
