1. Steganography
Rayan Ghamri

2. Introduction Steganography
from the Greek word steganos meaning “covered”
and the Greek word graphie meaning “writing”
Steganography is the process of hiding of a secret message within an ordinary message and extracting it at its destination
Anyone else viewing the message will fail to know it contains hidden/encrypted data

3. Cryptography VS Steganography
Steganography is the science of hiding information in such a way that no one suspects the information exists.
With cryptography the information is known to exist, but it is encoded in such a way that only the intended recipient can read it.
Steganography is usually combined with cryptography.

4. Continued

5. Steganography - Carrier Files
bmp
jpeg
gif
wav
mp3

6. Why Images? It is the most widely used medium being used today
Takes advantage of our limited visual perception of colors
This field is expected to continually grow as computer graphics power also grows
Many programs are available to apply steganography

7. Some tools: Steganos S-Tools (GIF, JPEG) StegHide (WAV, BMP)
Invisible Secrets (JPEG)
JPHide
Camouflage
Hiderman
And many others…

8. Why Images.. Digital images are made up of pixels
The arrangement of pixels make up the image’s “raster data”
8-bit and 24-bit images are common
The larger the image size, the more information you can hide.

9. Why Steganography…
Hiding data is better than moving it shown and encrypted.
To hide data in a popular object that will not attract any attention.
In case the data is extracted, it will be encrypted.

10. Steganography Techniques
Physical
Printed
Digital (Modern)

11. Examples in History (Physical)
Tattoos on shaved heads
Wax-covered tablets
Microdots – shrunken pictures
Invisible Inks - milk, fruit juice.

12. Printed Steganography
These messages were sent by the German embassy in World War I. This is called a null cipher.
PRESIDENT'S EMBARGO RULING SHOULD HAVE IMMEDIATE NOTICE. GRAVE SITUATION AFFECTING INTERNATIONAL LAW. STATEMENT FORESHADOWS RUIN OF MANY NEUTRALS. YELLOW JOURNALS UNIFYING NATIONAL EXCITEMENT IMMENSELY.
APPARENTLY NEUTRAL'S PROTEST IS THOROUGHLY DISCOUNTED AND IGNORED. ISMAN HARD HIT. BLOCKADE ISSUE AFFECTS PRETEXT FOR EMBARGO ON BYPRODUCTS, EJECTING SUETS AND VEGETABLE OILS.
Taking the first letter in each word of message 1 or second letter in message 2 reveals the hidden text.
PERSHING SAILS FROM NY JUNE 1.

13. Digital Steganography
Modern digital steganography
data is encrypted
then inserted and hidden, using a special algorithm which may add and/or modify the contents of the file
This technique may simply append the data to the file, or disperse it throughout
Carefully crafted programs apply the encrypted data such that patterns appear normal.

14. Example: Left image is original JPEG file
Right image is with hidden message

15. Methods for hiding data in Digital Image:
Least significant bit (LSB)
Discrete Cosine Transform (DCT)

16. Least significant bit (LSB)
Replaces least significant bits with the message to be encoded
Most popular technique when dealing with images
Simple, but susceptible to lossy compression and image manipulation

17. Example for LSB
The simplest and most common type of steganography is LSB (least significant bit). The one’s bit of a byte is used to encode the hidden information.
Suppose we want to encode the letter A (ASCII 65 or binary ) in the following 8 bytes of a carrier file.
becomes

18. RGB Color Model in Image Files
red, green, and blue light are added together in various ways to reproduce a broad array of colors.
(0, 0, 0) is black
(255, 255, 255) is white
(255, 0, 0) is red
(0, 255, 0) is green
(0, 0, 255) is blue
(255, 255, 0) is yellow
(0, 255, 255) is cyan
(255, 0, 255) is magenta

19. N color bytes = N *1/8 message bytes
Encoding Process
Step 1:
Convert image to pixels. Then these pixels split to R, G and B bytes
Step 2:
In this step secret message is converted to bytes.
Step 3:
Actual data hiding occurs when each bit of secret message is inserted to least significant bit of color byte. So one byte of message is inserted in 8 color bytes. By using this formula
N color bytes = N *1/8 message bytes

20. Example..

21. Example..

22. Methods of detecting Visual Detection (JPEG, BMP, GIF, etc.)
Audible Detection (WAV, MPEG, etc.)
Structural Detection - View file properties/contents
size difference
date/time difference

23. Decoding algorithm

24. Finally..
Steganography as a whole has existed in many forms throughout much of history.
Lossless compression of images with a great deal of color variation work best as a cover image to embed a message.
Steganography can be used as benefitial tool for privacy.