Fix Slow LUKS Decryption Mar 5th 2021 Words: 114

Problem

I have Linux installed with everything under /, which is on LUKS. The problem is, after entering the password, I have to wait for about 10 seconds before the GRUB menu shows up.

Test the decryption time. Note that under linux the decryption is fast but since grub uses a shitty implement, it will be much slower. 

1
sudo cryptsetup -v luksOpen --test-passphrase <device>

Show iterations count

1
sudo cryptsetup luksDump /dev/<partition>

MK iterations: 125547

Solution

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sudo cryptsetup -v luksChangeKey --iter-time 1000 /dev/<partition>

Make sure the key slot with the lower iteration is in the top slot.

Reference

How to change luks encryption difficulty on manjaro full disk encrypt