Image Steganography using LSB?

I have coded a LSB algorithm for Image Steganography. During retrieval process i'm getting different msg. Can anyone correct this code please!

Embedding code

    c = imread('image.bmp');
    message = 'hellokarthick'
    message = strtrim(message);
    m = length(message) * 8;
    AsciiCode = uint8(message); 
    binaryString = transpose(dec2bin(AsciiCode,8));
    binaryString = binaryString(:);
    N = length(binaryString);
    b = zeros(N,1); %b is a vector of bits
    for k = 1:N
        if(binaryString(k) == '1')
            b(k) = 1;
        else
            b(k) = 0;
        end
    end
    s = c;
    height = size(c,1);
    width = size(c,2);
    k = 1;
    for i = 1 : height
        for j = 1 : width
             LSB = mod(double(c(i,j)), 2);
            if (k>m || LSB == b(k))
                s(i,j) = c(i,j);
            else
                if(LSB == 1)
                    s(i,j) = c(i,j) - 1;
                else
                    s(i,j) = c(i,j) + 1;
                end
            k = k + 1;
        end
        end
    end
     imwrite(s, 'hiddenmsgimage.bmp');

Retriever coding

    s = imread('hiddenmsgimage.bmp');
    height = size(s,1);
    width = size(s,2);
    %For this example the max size is 100 bytes, or 800 bits, (bytes * = bits
    m = 800;
    k = 1;
    for i = 1 : height
        for j = 1 : width
            if (k <= m)
                b(k) = mod(double(s(i,j)),2);
                k = k + 1;
            end
        end
    end
    binaryVector = b;
    binValues = [ 128 64 32 16 8 4 2 1 ];
    binaryVector = binaryVector(:);
    if mod(length(binaryVector),8) ~= 0
        error('Length of binary vector must be a multiple of 8.');
    end
    binMatrix = reshape(binaryVector,8,100);
    display(binMatrix);
    textString = char(binValues*binMatrix);    
    disp(textString);

[supriya]

Hey KARTHICK,i tried to find the flaw in ur code but couldn't! Have u found it yet??

[gokul]

im working on the same code and experience same problem in decryption.. have u corrected d code. if so plz send me d correction.. plz do help me..

[arundhati guchait]

In the retrieving part, just do a change,

for k = 1 : m
     binaryVector(k) = b(k);
end

it will work.

thank u for the code. it helped us a lot.

[Abhishek Barla]

The code is correct except for one small change.

You never added the b(k) to the LSB. So, basically, you never encoded the message. Then how will you decode it?

In the encoding process, instead of this:

if (k>m LSB == b(k)) s(i,j) = c(i,j); else if(LSB == 1) s(i,j) = c(i,j) - 1; else s(i,j) = c(i,j) + 1; end k = k + 1;

You should have:

if (k>m LSB == b(k)) s(i,j) = c(i,j); else s(i,j) = c(i,j) + b(k); k = k + 1;

Everything else remains the same. It works!!

If anything else, then feel free to reply back to this comment. Hope it eases someone's life. Good luck!

[ARJUN K P]

the output of extraction is wrong...

pls help to to retrieve embedded data..

my email id : [e-mail]

[JIJO JOSE]

in the encoding part inside the two for loops make the following change and you can decode the message accurately,

            if(k<=m)
             LSB = mod(double(s(i,j)), 2);
             s(i,j)=s(i,j)+LSB+b(k);
             k=k+1;
            end

[Snehal Parekh]

I can not hide the text information more then one page by using this code.....so please some one help me for hidding the text information in image more than one page

[Walter Roberson]

Reshape() all of the pages together into a 2D array. Use this routine to hide the text. Reshape() back to 3D afterwards.

[Sahana Konchada]

we are geeting the error while running this code please suggest how to recover the codes

[Tommy Halim]

I just copying your code and I got error in my program, can you help me?

for i = 1 : height
        for j = 1 : width
             LSB = mod(double(c(i,j)), 2);

[Walter Roberson]

Tommy Halim, are you using the code posted by HARTHICK ? In that code, c would be the result of imread(), and imread() never returns a struct.

[Tommy Halim]

ah, sorry my fault. when read an image

c = imread('image.bmp');

I change it with

c = getframe(handles.axes1);

[Walter Roberson]

You will need c(index).cdata

[Tommy Halim]

I has been change from

c = getframe(handles.axes1);

to

c = getimage(handles.axes1);

[Walter Roberson]

getframe() takes a copy of whatever has been rendered into the frame, no matter what kind of graphics objects.

getimage() look specifically for image objects, such as created by image() or imagesc() or imshow() . Anything else that is part of the axes will be ignored.

[Tommy Halim]

Very helpful, thank you Walter Roberson

Answer 1

[Walter Roberson]

http://blogs.mathworks.com/videos/2010/09/02/using-debugger-to-walk-through-code/

[faiz ul amin]

% Access x y z coordinates and RGB color

% Read the point cloud from the 'Axle shaft.ply' file

ptCloud = pcread('Axle shaft.ply');

pcshow(ptCloud);

title('Axle shaft');

% Add labels to the axes

xlabel('X-axis');

ylabel('Y-axis');

zlabel('Z-axis');

% Access the location (coordinates) of all points in the point cloud

pointLocations = ptCloud.Location;

% Access the RGB color information of all points in the point cloud

pointColors = ptCloud.Color;

% Round the coordinates to the nearest integer

pointLocations = round(pointLocations);

% Display all points in the point cloud with RGB intensities

disp('All points in the point cloud (rounded to integers) with RGB intensities:');

disp([pointLocations, pointColors]);

disp('Axle shaft.ply');

[faiz ul amin]

dear walter roberson this is a code that i write for hiding data in 3d image.this code is not complete .i acces the points ,rgb intensity.now i hide the data in rgb intensity .i dont know how to complete code.

[Image Analyst]

@faiz ul amin If you have any questions, then ask them in a new discussion thread (not here), and attach your data and code to read it in with the paperclip icon after you read this:

TUTORIAL: How to ask a question (on Answers) and get a fast answer

Answer 2

[Maged Rawash]

it gives you different msg because you are using JPG and jpg using lossy mode to compress .. which change the pixel value and return different msg ..

you can use that code in imwrite();

imwrite(s,'img.jpg', 'Mode','lossless' );  

% not all image application will read JPG lossless

so just work on PNG, TIFF it works with me ...

to retrieve the correct massage without guessing the char number of the massage ... just store the msg length in first pixel and get it in retrieving code like this ....

c = imread(image);
c(1:1:1)= length(msg) ; %to count massage Char to easly retrive all the massage 
c=imresize(c,[size(c,1) size(c,2)],'nearest');
message = msg ; %add ' .' to prevint lossing one char  
message = strtrim(message);
m = length(message) * 8;
AsciiCode = uint8(message);
binaryString = transpose(dec2bin(AsciiCode,8));
binaryString = binaryString(:);
N = length(binaryString);
b = zeros(N,1);
for k = 1:N
  if(binaryString(k) == '1')
      b(k) = 1;
  else
      b(k) = 0;
  end
end
s = c;
  height = size(c,1);
  width = size(c,2);
k = 1;
for i = 1 : height
  for j = 1 : width
      LSB = mod(double(c(i,j)), 2);
      if (k>m || LSB == b(k))
          s(i,j) = c(i,j);
      elseif(LSB == 1)
          s(i,j) = (c(i,j) - 1);
      elseif(LSB == 0)
          s(i,j) = (c(i,j) + 1);
      end
  k = k + 1;
  end
end
imgWTxt = 'msgimage.png';
imwrite(s,imgWTxt);

----------------------------------- Retriever coding

s = imread(image);
height = size(s,1);
width = size(s,2);
m =  double( s(1:1:1) ) * 8  ;
k = 1;
for i = 1 : height
  for j = 1 : width
      if (k <= m)
          b(k) = mod(double(s(i,j)),2);
          k = k + 1;
      end
  end
end
binaryVector = b;
binValues = [ 128 64 32 16 8 4 2 1 ];
binaryVector = binaryVector(:);
if mod(length(binaryVector),8) ~= 0
error('Length of binary vector must be a multiple of 8.');
end
binMatrix = reshape(binaryVector,8,[]);
textString = char(binValues*binMatrix);
disp(textString);

thanks For the Code ...

[rini lya]

Retrieval coding

Your code works even when you comment the following lines and run

s = imread(image);
height = size(s,1);
width = size(s,2);
m =  double( s(1:1:1) ) * 8  ;
k = 1;
for i = 1 : height
  for j = 1 : width
      if (k <= m)
          b(k) = mod(double(s(i,j)),2);
          k = k + 1;
      end
  end
end

How is the hidden text retrieved then???

[rose del]

hello .. i'm looking for a code of styganography using linear codes like hamming or simplexe thnx .

[Walter Roberson]

That sounds like a university assignment that you would be expected to do your own work for.

[Naveen Gunnam]

thank you so much dude ,

[faiz ul amin]

dear walter roberson i need some help.i need code for my project.

project title:data hiddng using 3d image as cover.) i want to hide data in 3d image.

Answer 3

[supriya]

Actually wat i did is..made an array of the the positions of the pixels whose lsb wud be changed due to the encryption method and then did some changes in ur decryption method..see

   c = imread('C:\Documents and Settings\All Users\Documents\My Pictures\Sample Pictures\Sunset.jpg');
                  message = 'hellokarthick'
                  message = strtrim(message);
                  m = length(message) * 8;
                  AsciiCode = uint8(message); 
                  binaryString = transpose(dec2bin(AsciiCode,8));
                  binaryString = binaryString(:);
                  N = length(binaryString);
                  b = zeros(N,1); %b is a vector of bits
                  for k = 1:N
                      if(binaryString(k) == '1')
                          b(k) = 1;
                      else
                          b(k) = 0;
                      end
                  end
                  s = c;
                  height = size(c,1);
                  width = size(c,2);
                  k = 1; Array=[];l=1;my=1;
                  for i = 1 : height
                      for j = 1 : width
                           LSB = mod(double(c(i,j)), 2);
                          if (k>m || LSB == b(k))
                              s(i,j) = c(i,j);
                              l=k+1;
                          else 
                              if(LSB == 1)
                                  s(i,j) = c(i,j) - 1;
                              else
                                  s(i,j) = c(i,j) + 1;
                          Array(my)=l;
                          l=l+1;
                          my= my + 1;
                          end
                          k = k + 1;
                          end
                      end
                  end
                   imwrite(s, 'hiddenmsgimage.bmp');

 Retriever code changes:

k = 1;my=1;ur=1;
for i = 1 : height
  for j = 1 : width
    if( k<=m )
      if (my<numel(Array) && Array(my)==ur)
         b(k)=~(mod(double(s(i,j)),2));
      else
         b(k) = mod(double(s(i,j)),2);
      end
    k = k + 1;
    my= my + 1;
    end
  ur=ur+1;
  end
end

[supriya]

but all in vain!!

[Kailas]

why the msg converted is not in textual format.? plz tell me why u took binValues = [ 128 64 32 16 8 4 2 1 ]; and binMatrix = reshape(binaryVector,8,100);

[Pradeep Mallick]

Also I am facing this same problem i.e. ?? Error using ==> reshape To RESHAPE the number of elements must not change.

Error in ==> newsteganpgraphy at 97 binMatrix = reshape(binaryVector,8,100);

[Image Analyst]

Your binaryVector is not 800 elements. What does

numberOfElements = numel(binaryVector)  % no semicolon.

report?

[oleti kameswari]

I am not getting correct message

[Sahana Konchada]

I am getting while running the code in the line 29 as

Error using dec2bin Too many input arguments. Error in Receiverside (line 29) binaryString = transpose(dec2bin(AsciiCode,8));

what should I replace to get the correct output??

[Walter Roberson]

Which MATLAB version are you using? What shows up for

which -all dec2bin

[Hammad RIaz]

where to put this code, I need the complete code please. So far Not even a single submitted code worked for me. Can any body provide a single working code along with cover/ sego images please.

Retriever code changes:

k = 1;my=1;ur=1;

for i = 1 : height

for j = 1 : width

if( k<=m )

if (my<numel(Array) && Array(my)==ur)

b(k)=~(mod(double(s(i,j)),2));

else

b(k) = mod(double(s(i,j)),2);

end

k = k + 1;

my= my + 1;

end

ur=ur+1;

end

end

[Image Analyst]

@Hammad RIaz, here is a version to hide text:

https://www.mathworks.com/matlabcentral/fileexchange/54155-encoding-text-into-image-gray-levels?s_tid=srchtitle

and attached is a version for images, and for audio. I know they both work as-is. No guarantees after you start making any modifications of your own.

If you have trouble I suggest you start your own thread and post your code and data.

Answer 4

[ARJUN K P]

this code is not actally work correctly.. the extraction text is wrong...pls help me

the output is:

email: [e-mail]

[Image Analyst]

What's that garbage at the end? Don't paste all that stuff into the command window. Learn how to use a script.

Answer 5

[Mariam Chatha]

how would the code change if we were doing MSB?

[Walter Roberson]

MSB = c(i,j) / 128;

and the value to add or subtract would be 128 instead of 1.

[Shah]

I need the MATLAB code for MSB hiding text in image stegnography

[Image Analyst]

See my code for hiding in the LSB http://www.mathworks.com/matlabcentral/fileexchange/54155-encoding-text-into-image-gray-levels Of course if you hid it in the most significant bit, that would corrupt the image quite a bit. But nonetheless, you can use it to do that if you want.

Answer 6

[Aishwarya Rajan]

Can anyone please explain how the LSB embedding part of the above code works?

Answer 7

[Swati Nagpal]

Their is problem with the retrieval code it is showing different unexpected results. So if anyone got the correct result please do share the code. [e-mail]

Answer 8

[Muhammad Asfandyar Shahid]

please someone send correct code of image stegnography i will be thankfull

[Walter Roberson]

https://www.mathworks.com/matlabcentral/answers/?term=tag%3A%22steganography%22

[Muhammad Asfandyar Shahid]

i have code of lsb but in retrieving garbage data has come kindly correct it.

whats wrong in retrieving code??

s = imread('image1.jpg');
height = size(s,1);
width = size(s,2);
m =  double( s(1:1:1) ) * 8  ;
k = 1;
for i = 1 : height
  for j = 1 : width
      if (k <= m)
          b(k) = mod(double(s(i,j)),2);
          k = k + 1;
      end
  end
end
binaryVector = b;
binValues = [ 128 64 32 16 8 4 2 1 ];
binaryVector = binaryVector(:);
if mod(length(binaryVector),8) ~= 0
error('Length of binary vector must be a multiple of 8.');
end
binMatrix = reshape(binaryVector,8,[]);
textString = char(binValues*binMatrix);
disp(textString);

[Walter Roberson]

The most obvious problem you are having is that you are using jpg . jpg uses lossy compression unless you specifically ask otherwise, so the data you write into a jpg is not the data you get back out.

[Muhammad Asfandyar Shahid]

ok correct my code and send it back.

[Walter Roberson]

"ok correct my code and send it back."

No. I posted the link that will get you to a list of over 300 steganography postings. Some of them have complete code, and others have discussions of how you would need to deal with situations such as yours. I have no reason to do your work.

Answer 9

[Souradeep Mukhopadhyay]

% Clear the existing workspace 
clear all; 

% Clear the command window 
clc; 

% Read the input image 
input = imread('peppers.png'); 

% Convert image to greyscale 
input=rgb2gray(input); 

% Resize the image to required size 
input=imresize(input, [512 512]); 

% Message to be embedded 
message='geeksforgeeks'; 

% Length of the message where each character is 8 bits 
len = length(message) * 8; 

% Get all the ASCII values of the characters of the message 
ascii_value = uint8(message); 

% Convert the decimal values to binary 
bin_message = transpose(dec2bin(ascii_value, 8)); 

% Get all the binary digits in separate row 
bin_message = bin_message(:); 

% Length of the binary message 
N = length(bin_message); 

% Converting the char array to numeric array 
bin_num_message=str2num(bin_message); 

% Initialize output as input 
output = input; 

% Get height and width for traversing through the image 
height = size(input, 1); 
width = size(input, 2); 

% Counter for number of embedded bits 
embed_counter = 1; 

% Traverse through the image 
for i = 1 : height 
	for j = 1 : width 
		
		% If more bits are remaining to embed 
		if(embed_counter <= len) 
			
			% Finding the Least Significant Bit of the current pixel 
			LSB = mod(double(input(i, j)), 2); 
			
			% Find whether the bit is same or needs to change 
			temp = double(xor(LSB, bin_num_message(embed_counter))); 
			
			% Updating the output to input + temp 
			output(i, j) = input(i, j)+temp; 
			
			% Increment the embed counter 
			embed_counter = embed_counter+1; 
		end
		
	end
end

% Write both the input and output images to local storage 
% Mention the path to a folder here. 
imwrite(input, 'path_to_folder\originalImage.png'); 
imwrite(output, 'path_to_folder\stegoImage.png'); 

[Ishara Kariyawasam]

How to decrypt these??

[Walter Roberson]

There is a legal distinction between steganography, which "hides" data, and "encryption". If you need to decrypt data then you need to have encrypted it... and we cannot talk about encryption here for legal reasons.

Answer 10

[Hassan Vakani]

I know it is a quite late. First of all thank you for the code. Your logic doesn't have any problem. It is just the placement of the counter which is k=k+1. It should outside the outer if statement and it works.

for i = 1 : height
        for j = 1 : width
             LSB = mod(double(c(i,j)), 2);
            if (k>m || LSB == b(k))
                s(i,j) = c(i,j);
            else
                if(LSB == 1)
                    s(i,j) = c(i,j) - 1;
                else
                    s(i,j) = c(i,j) + 1;
                end
        end
k = k + 1;
        end
    end
     imwrite(s, 'hiddenmsgimage.bmp');

No need for adding the b(k) or anything else

Answer 11

[PoXiao]

Why did I run Retriever Coding and get garbled code instead of my original string, and how did I extract the original image and display it? I'm really at my wit's end

s = imread('C:\Users\hiddenmsgimage.png');    
height = size(s,1);
    width = size(s,2);
    m =  double( s(1:1:1) ) * 8  ;
    k = 1;
    for i = 1 : height
        for j = 1 : width
            if (k <= m)
                b(k) = mod(double(s(i,j)),2);
                k = k + 1;
            end
        end
    end
    binaryVector = b;
    binValues = [ 128 64 32 16 8 4 2 1 ];
    binaryVector = binaryVector(:);
    if mod(length(binaryVector),8) ~= 0
        error('Length of binary vector must be a multiple of 8.');
    end
    binMatrix = reshape(binaryVector,8,[]);
    textString = char(binValues*binMatrix);
    msgbox(textString, 'message');
   % disp(textString);
    

Answer 12

[Image Analyst]

See my attached demo.