Image and Key XORing

Hi there i am still stuck in xoring a 256 byte value with an image stored in a 3D array ? what should be the steps to do it ?I want to the store the first 256 bytes of the image and xor it with key then another 25 bytes of image with the same key and so on .I would later display my results in a figure ?

Any help would be greatly appreciated .

thanks

Answer 1

[Walter Roberson]

Untested:

t = reshape(YourImage(:), 256, []);
EncryptedImage = reshape( bsxfun(@xor, t, YourKey(:).'), size(YourImage) );

Of course you might have a rather different idea of what the "first" 256 bytes of an image are...

[Evolution]

thanks for the reply .i was checking the resize command and i got an error here . do i read the image correctly ?

x=imread('images.jpeg');

>> t = reshape(x(:), 256, []);

??? Error using ==> reshape

Product of known dimensions, 256, not divisible into total number of elements, 150540.

[Walter Roberson]

Correct. Your question did say what to do if your image was not divisible in to 256 byte groups, so I did not code for it.

xc = x(:);

nel = size(xc,1);

npad = mod(256 - mod(nel,256), 256);

xc = vertcat(xc, zeros(npad, 1));

t = reshape(xc, 256, []);

enct = bsxfun(@xor, t, YourKey(:).');

enct(end-npad+1:end) = [];

EncryptedImage = reshape( enct, size(x));

[Evolution]

thank a lot for the code .Its really helping me .Just before executing the bsxfun command i checked the values in variable passed in the function.

t has dimensions of 256x589 and yourkey(:).' has 1X256

After executing the function i got the error .

>> enct = bsxfun(@xor, t, r(:).');

??? Error using bsxarg: All non-singleton dimensions must match.

Error in ==> bsxfun at 100

[AX BX] = bsxarg(A,B);

I then swapped the variables

>> enct = bsxfun(@xor,r(:).',t);

??? Error using bsxarg: All non-singleton dimensions must match.

Error in ==> bsxfun at 100

[AX BX] = bsxarg(A,B);

again same error .

if its not too much can you help me with the error ?

thank you again for all the help.