I figured out there is a possibility that I can change the algorithm in the built-in cryptor, in the openSUSE install. The default algo loaded is AES and I want to change it to Twofish. I saw a post in gentoo's forums where it seems to be possible, although I don't know if I can do the graphic install after it nor how to procceed.

The command would be similar to:

What should I do? How to install the system afterwards? (with graphical install). Also, is there a way to check the encryption description after the system install?

I want to install openSUSE 12.3

Having dome something similar myself I can tell you that I had to manually change the encryption algorithm during the setup of a debian-based system. Basically when you reach the screen that asks you to partition the hard disk you should switch to a console and manually partition the disks + setup crypto and LVM. Then switch back to the graphical interface, refresh the disk layout and assign the mountpoints. Finally I had to update fstab and crypttab before updating initramfs.

Here's what I used to encrypt:
cryptsetup -c aes-xts-plain64 -h sha512 -s 512 -y --use-random -i 5000 luksFormat /dev/sdXY

I am not sure how it works on openSUSE, but on debian the decryption was automatic. All you need to make sure is that the appropriate modules are loaded (depending on what crypto you use)... aes, sha512, serpent, twofish, etc.

How do I do that in openSUSE?