class String
    def mngcrypt
        newstring = ""
        self.length.times do |i|
            newstring = newstring + (self.slice(i) ^ ((0x05 + (0xC1 * i)) % 0xFF)).chr
        end
        return newstring
    end
end

mng = File.new("ds_music.mng", 'rb')
mng.seek(4)
scriptpos = mng.read(4).unpack("V")[0]
scriptlen = mng.read(4).unpack("V")[0]
mng.seek(scriptpos)
encscript = mng.read(scriptlen)
p encscript.mngcrypt