steganography rayan ghamri. introduction steganography from the greek word steganos meaning...
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Steganography
Rayan Ghamri
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
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.
Continued
Steganography - Carrier Files
bmp
jpeg
gif
wav
mp3
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
Some tools: Steganos
S-Tools (GIF, JPEG)
StegHide (WAV, BMP)
Invisible Secrets (JPEG)
JPHide
Camouflage
Hiderman
And many others…
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.
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.
Steganography Techniques
Physical
Printed
Digital (Modern)
Examples in History (Physical)
Tattoos on shaved heads
Wax-covered tablets
Microdots – shrunken pictures
Invisible Inks - milk, fruit juice.
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.
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.
Example:Left image is original JPEG file
Right image is with hidden message
Methods for hiding data in Digital Image:
Least significant bit (LSB)
Discrete Cosine Transform (DCT)
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
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 01000001) in the following 8 bytes of a carrier file.
01011101 11010000 00011100 10101100
11100111 10000111 01101011 11100011
becomes
01011100 11010001 00011100 10101100
11100110 10000110 01101010 11100011
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
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
Example..
Example..
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
Decoding algorithm
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.