I think it's more appropriate to display Unlock rather than Decrypt on luks volumes, because it may seem that changes are permanent.
Git commit 40f59a487027b27eb5d04971fae8213792fb0733 by Andrius Štikonas. Committed on 23/04/2018 at 08:05. Pushed by stikonas into branch 'kauth'. Rename LUKS open and close Labels to "Lock" and "Unlock" M +2 -2 src/fs/luks.cpp https://commits.kde.org/kpmcore/40f59a487027b27eb5d04971fae8213792fb0733