Steganography using matlab

www.spiroprojects.com




1.Message Analyzed: Determine message type (image or text) and dimensions (Width/Height for images; Length for text).
o Color Images are converted to be Grayscale Images
2.Header Prepared: Header data added to beginning of message for Decoding Step.
o Image Header Format: 4 digits of Width Dimension followed by 4 digits of Height Dimension
o Text Header Format: 't' followed by 7 digits of Length Dimension

3.Encryption Applied: Header and Message encrypted using symmetric XOR encryption key.
4.Message Encoded: Encrypted Header/Message encoded onto Cover Medium.
 



        1.  Message Decoded: 
           §   Header decoded/decrypted first to determine recovery cycles needed.   
           §   Algorithm recovers encrypted Message data.  
        2.  Message Decrypted: Message decrypted using same symmetric XOR encryption key used 
          earlier.   
        3.Message Recovered: Message put into viewable format. 
           §   Text Messages saved directly to .txt files. 
           §   Image Messages require dimensions from header to be put into .bmp files. 



      2. Sequential vs Pseudo-Random Encoding/Decoding
          
         Sequential Encoding/Decoding

              Process:
1.      Message Data is Encoded/Decoded from some starting point
(Typically upper left pixel)
2.      Message Data is then Encoded/Decoded in a set unvarying pattern
(Typically to adjacent pixels)


             Advantages:
·         Simple to Implement
             Disadvantages:
·         Easily Detected using Histogram Analysis
(Can also detect Message Size Directly)
 
·         Slow and Tedious Recovery
(Usually implemented using counters; slows recovery process)
·         Repeatable Encoding Method DECREASES Effectiveness of any Encryption Techniques




         Pseudo-Random Encoding/Decoding
              Process:
1.      Pseudo-Random Number Generator Initialized
(typically no set starting point)
2.      Message Data is then Encoded/Decoded based upon the pixel location determined by Random Number Generator
(typically no set pattern)
             Advantages:
·         No set Encoding/Decoding Pattern for Histogram Analysis to Detect
·         Quicker Recovery Rate
(Usually implemented by Pre-Defining encoding pattern; more efficient for recovery process)
·         Message size difficult to estimate
            Disadvantages:
·          Detectable using varying sized windows and localized Histogram Analysis




            





Previous
Next Post »