Wednesday, 24 December 2014

MATLAB code for High capacity steganography for binary image and text.

This code embeds one and more than one bits in single pixel of color image. Secrete image and secrete message at a time embedded into color cover image. 
Cover Image: 
Given cover image is a Color image
Let 'A' is an original image having size 'm*n*p' represented as

Secrete Message:

Let 'w' be the secrete binary image having size 'r*c' represented as

This 2D secrete binary image is converted into 1D array and size of that array is '1*(r*c)' and represented as

Let 'g' be the secrete message in text. This message is 1st converted into binary 1D array and represented as

Secrete Key:
Two secrete keys are defined one for 'sec_array' and one for 'sec_msg_array'. Secrete key is a binary array and represented as

Step 1: Encryption of secret messages

Secrete key and secrete messages are 1st xored with each other’s i.e.

Step 2: Appending of enc_sec_img and enc_sec_msg

Step 3: Actual embedding:
Variable length least significant bit substitution: 
The principle involved in this method is to replace all mentioned LSB bits of pixels of the cover image with secret bits. This method embeds the variable-length secret bits in the same variable length LSBs of pixels.
Simple example of single bit substitution is as follows.

Fig : LSB Substitution (a) Image having size 2*2, (b) Binary format of image (a), (c) Binary secret data, (d) LSB substitution-embedding (c) into (b), (e) Final image after substitution

Above figures shows you detailed information about LSB substitution method. Figure (a) is a original image having size of 2*2. Figure (b) shows binary format of image. Figure (c) is a secret image; this image will be embedded into (b). Figure (d) is a stego object in which secret data is embedded. Embedded data is indicated by bold font and finally figure (e) is a modified image after embedding process. 

Step 4: Extraction Process:

1. This operation is exactly inverse to that of embedding operation.
2. Extract number of encrypted bits from stego image.
3. Use encryption key that we used at the sender side.
4. Now xor secrete key with encrypted bits. Use secrete key that we used at the sender. 

In this way we can recover secrete messages at the receiver.

MATLAB Implementation:
Main GUI:
Sender GUI: 
Receiver GUI:

Video of the code

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