[dm-crypt] Pass+keyfile

Quentin Lefebvre qlefebvre_pro at yahoo.com
Mon Dec 1 14:49:54 CET 2014


I guess his point was to build something like a strong authentication with:
(1) something that I *own* (a key, maybe on a USB key),
(2) something that I *know* (a passphrase).

This doesn't look too bad to me.

But maybe it's worth remembering hash algorithms are ignored with key 
files in plain mode, so that the --hash=sha512 is not effective and 
actually equivalent to --hash=plain in this case.

Best regards,

Le 01/12/2014 13:49, Arno Wagner a écrit :
> This construction is redundant and does not provide any
> additional security as compared to passphrase alone,
> assuming that your passphrase is secure.
> If your passphrase is insecure, you should fix that
> instead.
> Arno
> On Mon, Dec 01, 2014 at 03:54:19 CET, 0x14 at openmailbox.org wrote:
>> Hi there, is this construction secure? Assuming "keyfile" is a file
>> and "/dev/device" is a block device, both made with /dev/urandom.
>> cryptsetup open --hash=sha512 --cipher=aes-xts-plain64 --type=plain
>> keyfile keyfile_tmp && cat /dev/mapper/keyfile_tmp | \
>> cryptsetup open --hash=sha512 --cipher=aes-xts-plain64 --type=plain
>> --key-file=- /dev/device cryptodevice && \
>> cryptsetup close keyfile_tmp && mount /dev/mapper/cryptodevice
>> /media/cryptodevice
>> The goal is to use pass+keyfile to decrypt storage. I put it in a
>> script and it works as it should at a glance. Are there alternatives
>> or improvements? Stupid errors maybe?
>> Thanks.

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