image scrambling using arnold scramble

does anyone knows about arnolg's image scrambling ? i am scrambling an image using arnold scramble as :

 wname='_copyright.bmp';
 I=imread(wname);
 [rown,coln]=size(I);
 ct=input('Enter Key');
 for inc=1:ct
    for row=1:rown
        for col=1:coln

            nrowp = row;
            ncolp=col;
            for ite=1:inc
                newcord =[1 1;1 2]*[nrowp ncolp]';
                nrowp=newcord(1);
                ncolp=newcord(2);
            end
            arnold(row,col)=I((mod(nrowp,rown)+1),(mod(ncolp,coln)+1));

        end
    end

end

can anyone plz tell how to get back original image by applying reverse arnold scramble ???

[Manpreet]

Please explain the code for the key.