Description of steganography mechanism and compressed or uncompressed image.

1. Steganography
Prof. Neeraj Bhargava
Kapil Chauhan
Department of Computer Science
School of Engineering & Systems Sciences
MDS University, Ajmer

2. Introduction
• Form of Communication
1. Cryptography
• Scrambles the message into cipher
2. Steganography
• Hides the message in unexpected places
• Digital Applications of Steganography
1. Can be hidden in digital data
• MS Word (doc)
• Web pages (htm)
• Sound files (mp3)
• Video files (mpeg, avi)
• Digital images (bmp, gif, jpg)

3. Background
Uncompressed Images
Grayscale Bitmap images (bmp)
 256 shades of intensity from black to white
 Can be obtained from color images
 Arranged into a 2-D matrix
 Messages are hidden in the least significant bits (lsb)

4. Introduction
Compressed Images
Grayscale jpeg images (jpg)
 Joint Photographic Experts Group (jpeg)
 Divides into 8x8 blocks
 Huffman Coding
 Affects the images statistical properties

5. Finding and Extracting Messages
from Bitmaps
Problem
Messages can be hidden
May be anywhere in image
Cannot see message in image
Would take forever to be processed by a human

6. Finding and Extracting Messages from
Bitmaps
Conclusion
Messages are detectible and extractible from non-encrypted
uncompressed images.
Linear messages can be found in any direction with more
computation

7. Finding and Extracting Messages from
Bitmaps
Conclusion
Messages are detectible and extractible from non-encrypted
uncompressed images.
Linear messages can be found in any direction with more
computation