unpackimg Compression used: data Error!

Hello Comunity:)

I want to play around with my own build of Cyanogenmod. I have an not yet supported (Mediatek) device and want to give it a try... (It probably will not work and I will hardbrick my device but thats better than just throw it away and buy a new smartphone because mine is quite old).

I have the stock ROM already with the boot.img and recovery.img and a Windows version of Android Kitchen which contains unpackimg.

Now I tried to unpack an image (I tried both boot.img and recovery.img) but it gives an error:

Code:

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Android Image Kitchen - UnpackImg Script
by osm0sis @ xda-developers

Supplied image: boot-sign.img

Removing old work folders and files . . .

Setting up work folders . . .

Splitting image to "/split_img/" . . .

BOARD_KERNEL_CMDLINE
BOARD_KERNEL_BASE 10000000
BOARD_NAME 1392980983
BOARD_PAGE_SIZE 2048
BOARD_KERNEL_OFFSET 00008000
BOARD_RAMDISK_OFFSET 01000000
BOARD_TAGS_OFFSET 00000100

Unpacking ramdisk to "/ramdisk/" . . .

Compression used: data
Error!

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Then I read about "lokied" images, which seem to be protected somehow. Because of that I downloaded the Loki-Addon and tried unlokimg. That gives me a new image which results in the same error as above.

Sorry, but for some reason I am not allowed to add links to this post, maybe because I am a new user...
But the program I used could be found in [DEV][TOOL] Android Image Kitchen - Unpack/Repack Kernel Ramdisk [Win/Android/Linux] by osm0sis.

Is this a common error and is there any way to use those images for building my own Cyanogenmod?