Unable to auto-mount encrypted filesystem.squashfs of Debian Live CD

Part 1 I've created a live ISO image of my system using 'live build' tool on a Debian system. For automated installation i've used a preseeding file. To protect my senstive data I'm using LUKS encryption to encrypt the squashfs file of the ISO and the process is as follow - Extract the IOS image. Create a LUKS encrypted container. Put the unencrypted filesystem.squashfs file into the container. Rename the container to filesystem.squashfs. Recreate the ISO image. I've tried this method but was unsuccessful. During the installation the system shows an error 'could not find filesystem.squashfs' After some googling I found that the boot process should be - ...the encrypted filesystem.squashfs is mounted in the memory then it will asks for a password which will decrypt the encrypted filesystem.squashfs and then rest of the boot process resumes normally. The problem is that I don't know how I can make the encrypted squashfs mount in the memory during the installation process. I've found this link https://askubuntu.com/questions/1041916/booting-encrypted-squashfs-from-live-cd which performs similar functionality on an Ubuntu system. In ubuntu, the 'casper' tool is used for creating live cd which creates 'script' files in initrd of the ISO. In the above link we can see that a file named 'casper-helper' is edited to tell the system to mount the encrypted squashfs during the boot process. But I couldn't find its alternative on the debian system. Any help is welcome. Part 2 Is it possible to attain automatic decryption as I want fully automated installation I don't want it to ask for the password. Somehow if I can save a keyfile in the ISO which will decrypt it automatically during installation. If yes then please help