[dm-crypt] Can I test for LUKS passphrase strength without formatting a device?

Michael Kjörling michael at kjorling.se
Tue Nov 7 22:12:45 CET 2017

On 7 Nov 2017 17:51 +0100, from jtulak at redhat.com (Jan Tulak):
> Is it possible to test whether a passphrase is strong enough (and
> luksFormat will accept it), without the need to really create a device
> with this passphrase? I ask because I want to test the password before
> I run a sequence of commands and I don't want them to fail in the
> middle just because of a weak passphrase.

Adding to Milan Broz's answer, you can always use a simple file (or a
sparse file) as a backing device for a LUKS container. Doing so will
also tell you that the utilities can understand all other options
you're feeding them, which may be a consideration if you are providing
custom settings (for example, hash algorithm, encryption algorithm,
etc.). Just remember to close the container before you delete the

Michael Kjörling • https://michael.kjorling.semichael at kjorling.se
                 “People who think they know everything really annoy
                 those of us who know we don’t.” (Bjarne Stroustrup)

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