Thanks Arno, your pointer helped me resolve my problem, which was due to a newline being appended by '<<<'. I successfully created a key file with $ echo -n 'password' | openssl dgst -sha512 -binary > keyfile What really helped was your suggestion to view the key from dm-crypt, which I did like this $ dmsetup table --target crypt --showkey /dev/mapper/mydisk That showed me what the SHA1 was and, once I knew that, I could compare what I was generating with it and quickly realised the difference was probably a terminating end-of-line character. Many thanks to you. John On 07/11/14 18:56, Arno Wagner wrote: > 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. I had read that, specifically the part "From a Key File" which is why I believed I needed a binary key. > > 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. Yes, I was aware of that but just tried it in case I was wrong about it being a binary key. My other attempt (the openssl one) produces a binary key but didn't work for me. I now know that was due to the here-string <<< appending a newline. > > 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 _______________________________________________ dm-crypt mailing list dm-crypt@xxxxxxxx http://www.saout.de/mailman/listinfo/dm-crypt
