Alternative to supervivi in NOR

Hi all...

I have a mini2440 128M board. I am using nboot bootloader in NAND and
windows ce. Now i want to protect access to supervivi in NOR to prevent
some one make changes to NAND. As supervivi source code is not publicly
available i can not make changes to it.
Anyone one knows an alternative to supervivi in NOR with available source
code?

Thanks.