Issues encrypting root partition with Luks

I was given a "golden image" of an out of date production server and was instructed to update and harden the OS for production delivery. The issue I am running into is that LUKS. I am using Suse 12.5. When booting into an Ubuntu live CD to encrypt the root partition I get an error. * There are 8 total partitions. The root (system) is on sda3. * The command I am running is as follows:

-shell
    cryptsetup reencrypt /dev/sda3 --new --reduce-device-size 32m --type luks1

* The error that is returned is:

WARNING: Device /dev/sda3 already contains a 'dos' partition signature.
    Device /dev/sda3 contains broken LUKS metadata. Aborting operation.

* Running blkid /dev/sda3 returns

LABEL="SYSTEM" UUID=too long to type BLOCK_SIZE="4096" TYPE=ext4 PT type=dos partlable=primary partyuid=too long to type

I am using LUKS1 because I have read that GRUB only works with LUKS1 encryption. Any help or another route would be greatly appreciated. **Update:** I am still actively looking for a solution to encrypt an existing filesystem. If anyone has a different option I am willing to try that. My next idea is completely rebuilding the filesystem using a new hard drive, shuffling the data over. Will that sort of thing work? Still trying to get a good solution.