Hello Milan,

Yes, I have the module installed and enabled.


# lsmod | grep -i gcm

gcm                    24576  0


# modprobe gcm


# modinfo gcm

filename:       /lib/modules/4.1.12-61.1.19.el7uek.x86_64/kernel/crypto/gcm.ko

alias:          crypto-gcm

alias:          gcm

alias:          crypto-rfc4543

alias:          rfc4543

alias:          crypto-rfc4106

alias:          rfc4106

alias:          crypto-gcm_base

alias:          gcm_base

author:         Mikko Herranen <mh1@iki.fi>

description:    Galois/Counter Mode

license:        GPL

srcversion:     0805471CE9244CDA1D08732

depends:

intree:         Y

vermagic:       4.1.12-61.1.19.el7uek.x86_64 SMP mod_unload modversions

signer:         Oracle CA Server

sig_key:        99:0C:6B:AD:6E:20:40:AB:2F:AC:19:2B:13:86:80:73:E1:2A:95:FB

sig_hashalgo:   sha512


#cryptsetup luksFormat --type luks2 /dev/sdb2 --cipher aes-gcm-random --integrity aead


WARNING!

========

This will overwrite data on /dev/sdb2 irrevocably.


Are you sure? (Type 'yes' in capital letters): YES

Enter passphrase for /dev/sdb2:

Verify passphrase:

Cipher aes-gcm-random (key size 256 bits) is not available.

#

Vinay
On 28 Feb 2020, 4:51 PM +0530, Milan Broz <gmazyland@gmail.com>, wrote:
On 27/02/2020 06:37, vinay paduru wrote:
I am trying to encrypt a volume with *LUKS2* *AES-GCM-Random* cipher
and I am seeing an error saying “key size 256 bits” not available. I
tried changing the key size but same error repeats for whatever the
key size we give.

Do you have kernel with gcm crypto module enabled?

Milan