www.pudn.com > encryption.rar > encryption.m

function encryption(string1, string2, x0, y0) 
%ENCRYPTION encrypt the input image 
 
if nargin < 2 
    error('not enough input arguments.'); 
end 
 
if nargin < 3 | isempty(x0) 
    x0 = 0.10384; 
else 
    if sum(size(x0)) > 2 
        error('x0 must be scalar.'); 
    end 
end 
 
if nargin < 4 | isempty(y0) 
    y0 = 0.80637; 
else 
    if sum(size(y0)) > 2 
        error('y0 must be scalar.'); 
    end 
end 
 
img1 = imread(string1); 
img2 = imread(string2); 
S1 = size(img1); 
S2 = size(img2); 
 
if length(S1) ~= 3 | length(S2) ~= 3 | S1(1) ~= S2(1) | S1(2) ~= S2(2) | S1(3) ~= S2(3) 
    error('the two input image should be the same size M x N x 3.'); 
end 
 
figure; 
subplot(2,2,1); 
imshow(img1,[]); 
title('A image'); 
 
subplot(2,2,2); 
imshow(img2,[]); 
title('B image'); 
 
R = S1(1); 
C = S1(2); 
r = mod(S1(1), 8); 
c = mod(S1(2), 8); 
 
%padding 
if r ~=0 || c ~=0 
    img1 = padarray(img1, [(8-r) (8-c)], 'post'); 
    img2 = padarray(img2, [(8-r) (8-c)], 'post'); 
end 
 
S3 = size(img1); 
num = S3(1)*S3(2); 
X = zeros(num, 1); 
Y = zeros(num, 1); 
X(1) = x0; 
Y(1) = y0; 
 
%cut the beginning digital 
for i = 1:100 
    X(1) = 1 - 2*X(1).^2; 
    Y(1) = 1 - 2*Y(1).^2; 
end 
 
%logistic serials 
for i = 2:num 
    X(i) = 1 - 2*X(i-1).^2; 
    Y(i) = 1 - 2*Y(i-1).^2; 
end 
 
%chaotic matrix 
[X1 x1] = sort(X); 
X2(x1) = 1:num; 
X3 = reshape(X2, S3(1), S3(2)); 
 
%symbol matrix 
Y1 = zeros(num, 1); 
Y2 = Y1 <= Y; 
Y3 = reshape(Y2, S3(1), S3(2)); 
 
%encryption in space domain 
% permutation of A 
for i = 1:S3(1) 
    for j = 1:S3(2) 
        l = mod(X3(i, j), S3(2)); 
        if l == 0 
            l = S3(2); 
        end 
        k = (X3(i, j) - l) / S3(2) + 1; 
        temp = img1(i, j, :); 
        if X3(i, j) >= num / 2 
            img1(i, j, :) = img2(k, l, :); 
            img2(k, l, :) = temp; 
        else 
            img1(i, j, :) = img1(k, l, :); 
            img1(k, l, :) = temp; 
        end 
    end 
end 
 
%permutation of B 
for i = 1:S3(1) 
    for j = 1:S3(2) 
        l = mod(X3(i, j), S3(2)); 
        if l == 0 
            l = S3(2); 
        end 
        k = (X3(i, j) - l) / S3(2) + 1; 
        temp = img2(i, j, :); 
        if X3(i, j) >= num / 2 
            img2(i, j, :) = img1(k, l, :); 
            img1(k, l, :) = temp; 
        else 
            img2(i, j, :) = img2(k, l, :); 
            img2(k, l, :) = temp; 
        end 
    end 
end 
 
% %encryption in DCT domain 
% img1 = double(img1) / 255; %important 
% img2 = double(img2) / 255; 
%  
% %DCT 
% for k = 1:S3(1)/8 
%     p = (k-1)*8+1; 
%     for l = 1:S3(2)/8 
%         q = (l-1)*8+1; 
%         temp1 = zeros(8, 8, 3); 
%         temp2 = zeros(8, 8, 3); 
%         for u = 0:7    
%             for v = 0:7    
%                 if u == 0 
%                     Cu = 1/sqrt(2); 
%                 else 
%                     Cu = 1; 
%                 end 
%                  
%                 if v == 0 
%                     Cv = 1/sqrt(2); 
%                 else 
%                     Cv = 1; 
%                 end 
%                  
%                 for i = 0:7 
%                     for j = 0:7 
%                         temp1(u + 1, v + 1, :) = temp1(u + 1, v + 1, :) + 0.25*Cu*Cv*img1(p+i, q+j, :)*cos(3.1415926*(2*i+1)*u/(2*8))*cos(3.1415926*(2*j+1)*v/(2*8)); 
%                         temp2(u + 1, v + 1, :) = temp2(u + 1, v + 1, :) + 0.25*Cu*Cv*img2(p+i, q+j, :)*cos(3.1415926*(2*i+1)*u/(2*8))*cos(3.1415926*(2*j+1)*v/(2*8)); 
%                     end 
%                 end 
%             end 
%         end 
%         img1(p:(p+7), q:(q+7), :) = temp1; 
%         img2(p:(p+7), q:(q+7), :) = temp2; 
%     end 
% end 
 
% row of A 
for i = 1:S3(1) 
    for j = 1:S3(2) 
        temp = img1(i, :, :); 
        if Y3(i, j) == 1 
            img1(i, :, :) = img2(i, :, :); 
            img2(i, :, :) = temp; 
        end 
    end 
end 
 
% column of B 
for i = 1:S3(1) 
    for j = 1:S3(2) 
        temp = img2(:, j, :); 
        if Y3(i, j) == 1 
            img2(:, j, :) = img1(:, j, :); 
            img1(:, j, :) = temp; 
        end 
    end 
end 
 
% %IDCT 
% for k = 1:S3(1)/8 
%     p = (k-1)*8+1; 
%     for l = 1:S3(2)/8 
%         q = (l-1)*8+1; 
%         temp1 = zeros(8, 8, 3); 
%         temp2 = zeros(8, 8, 3); 
%         for i = 0:7     
%             for j = 0:7  
%                 for u = 0:7 
%                     for v = 0:7 
%                         if u == 0 
%                             Cu = 1/sqrt(2); 
%                         else 
%                             Cu = 1; 
%                         end 
%                          
%                         if v == 0 
%                             Cv = 1/sqrt(2); 
%                         else 
%                             Cv = 1; 
%                         end 
%                         temp1(i + 1, j + 1, :) = temp1(i + 1, j + 1, :) + 0.25*Cu*Cv*img1(p+u, q+v, :)*cos(3.1415926*(2*i+1)*u/(2*8))*cos(3.1415926*(2*j+1)*v/(2*8)); 
%                         temp2(i + 1, j + 1, :) = temp2(i + 1, j + 1, :) + 0.25*Cu*Cv*img2(p+u, q+v, :)*cos(3.1415926*(2*i+1)*u/(2*8))*cos(3.1415926*(2*j+1)*v/(2*8)); 
%                     end 
%                 end 
%             end 
%         end 
%         img1(p:(p+7), q:(q+7), :) = temp1; 
%         img2(p:(p+7), q:(q+7), :) = temp2; 
%     end 
% end 
%  
% img1 = im2uint8(img1); %important 
% img2 = im2uint8(img2); 
 
subplot(2,2,3); 
imshow(img1,[]); 
title('encrypted image of A'); 
imwrite(img1, 'encrypted-A.jpg'); 
 
subplot(2,2,4); 
imshow(img2,[]); 
title('encrypted image of B'); 
imwrite(img2, 'encrypted-B.jpg');