Please Help Me. Can I Get a Matlab Code for Image Steganography Using Channel Differences

Hello everyone.. I have final project about steganography with algoritm Vibrant Color. Technique of this algoritm are :

1. Use one of the three channels as the indicator. The indicator sequence can be made random, based, on a shared key between sender and receiver.
2. Data stored in one of the two channels other than the indicator. The channel whose color value is lowest among the two channels other than that of the indicator, will store the data in its least significant bits.
3. Instead of storing a fixed number of data-bits per channel, variable numbers of bit are to be stored depending on the color value of the channel. The lower the value, the higher the data-bits to be stored.
4. To retrieve data, need to know which channel stores the data-bits. This is done by looking at the least significant bits of the two channels other then the indicator : # if the bits are same, then the channel following the indicator in cyclic order stores the data. Otherwise, the chaannel which precedes the indicator in cyclic order stores the data.
5. Therefor, we needed modified last bit of channel other indicator channel and channel with data. Do this process if needed.

Help please..

[Image Analyst]

What kind of help do you want? Do you want us to write the whole thing for you and give you our code to turn in?

[Nurmi]

Please can you give me code from the first process, about determination the channel indikator. The indicator sequence can be made random, based, on a shared key between sender and receiver. To determine the indicator, a key modulus 3, if key mod 3 = 1 then channel indikator is red, if key mod 3 =2 then channel indikator is green, if key mod 3 = 3 then channel indikator is blue. I have a part of code to encoding

function [I] = encode(img,msg,key)
  % encode : this function to hide a message in to image

msg_type = ischar(msg); % message is text
msg_tem = double(msg);  
msg_dim = num2str(length(msg_temp));
msg_length = length(msg_dim);
z = 0;
if msg_length < 7
    padtext = 7 - msg_length;
    for z = 1:padtext;
    msg_dim = horzcat('0',msg_dim);
    end
    msg_head = horzcat('t',msg_dim);
    msg_temp_head = horzcat(msg_head,msg_temp);
end

% Key
  ind = mod(uint8(key),3); %key is shared key, have been called on prev func
msg_ind = ind;

 % Cover Image
   cover_img = im2uint8(img); %img is cover image, have been called on prev func
   ....

How proceed the code to determine channel indicator?

[Walter Roberson]

key mod 3 can never equal 3.

[Nurmi]

sorry, I mean 0, if key mod 3 = 0 channel ind is blue

Answer 1

[Image Analyst]

To get a random number between 1 and 3, use randi:

key = int32(randi(3, 1))

then do the mod thing, like you already have, except I made key an integer so you don't need to call uint8().

ind = mod(key,3);

If that what you mean?

[Nurmi]

key will be entered before encoding process :

%%Input Key
  key = input('\nEnter Between 1 - 100:\n');
  if key < 1 || key > 100
      error('Invalid');
  end

    key = uint8(key);

and then i wanna using the key to encoding process by modulus.

[Image Analyst]

OK. Good luck.