chaotic(tent map ) decryption

hello everyone

I've wrote code to encrypt image by using chaotic system tent map and it works

but i don't know how to dycrypt the image (I've use XOR with encryption )

i tried xor with decryption but it didn't work

so please may someone help me with that

here is the code;

I = imread('lena.bmp');

[ a , b , c ] = size (I); 
N = a*b*c ;


u = 1.99;     %initial value 


x = linspace(0,1,N);    % create a vector of x-positions

 
outputs = zeros(size(I));
for ii = 1 : numel(I)

   
    
    if x(ii) < 0.5 
       Y(ii)=u*x(ii); 
       
    elseif x(ii) >= 0.5
        Y(ii)=u*(1-x(ii)); 
        
        
        outputs(ii) = Y(ii);
      
    end
   
end



TR = outputs > (100/256);

II = double (I);
I2D = II > (100/256); % images of type double are in the range 0 to 1.(SO NO NEED TO CONVERT IT BINARY)

XXX= xor(TR,I2D);

XR =double (XXX) ;

 
figure(1);
imshow(I)
title('input image')


figure(2);
imshow(XR)
title('encrypted image ')

algorithm :

The chaotic tent map is given by:

we use the chaotic tent map to implement encryption process. The image encryption algorithm proposed in this paper consists of the following major steps:

• Read plain-images (original image) (Ma×bMa×b), get size of M, e.g., use [a, b, c] to save the size of M, a=256a=256, b=256b=256, c=3c=3, let N=a∗b∗cN=a∗b∗c, and initiate control parameter (μμ) of the chaotic tent map;

• Input the secret (encryption) key x0x0 into the algorithm. Iterate the chaotic tent map N times using system (2), and obtain the key array x(n), the size of x(n) is N;

• Encrypt each element of matrix (Ma×bMa×b) using the key array x(n), that is, mix the original image (Ma×bMa×b) components with the key array x(n);

• The resulting image of step (3) is the ciphered image.