Steganography is the practice of hiding secret messages within other non-secret files or messages. The document discusses different techniques for digital steganography, including least significant bit modifications to hide messages in image pixel values, as well as masking/filtering and transformations in frequency domains. Lossless image compression works best for cover images to embed secret messages stealthily. While steganography has legitimate uses, it can also enable covert or illegal communications if abused.

1. Steganography
NAME --Santu Chall
Roll No – 001130401005
Dept. – School of Education Technology
Course – Master in Multimedia Development

2. What is Steganography ?
• Comes from greek
‘steganos’ – covered
‘graphie’ – writing
• Steganography is the art and science of
writing hidden messages in such a way
that no one apart from the intended
recipient knows of the existence of the
message.
• Carrier: text, image, video, audio, etc.
Stegosaurus: a covered lizard
(but not a type of cryptography)

3. What is Computer Image
• Computer image is an array of pixels
• Pixels represent different light intensities
Are encoded as bit patterns
• Bit-depth
8bit grayscale – 256 levels of gray
24bit RGB – 16,777,216 million colors

4. Image Compression
• Lossy vs Lossless Compression
• Lossy (JPEG)
Discards excess image data, removes details that are too
small for human eye to differentiate.
Smaller file size.
• Lossless (TIF,BMP,GIF)
No loss of data, uncompressed image bit-by-bit identical
to original.
Larger file size.

5. Steganography Techniques
• Least-significant bit modifications(LSB)
• Masking and filtering
• Transformations

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

7. Uses of LSB
• Storing passwords and/or other confidential
information
• Covert communication of sensitive data
• Speculated uses in terrorist activities
• Being widely used to hide and/or transfer
illegal content

8. MASKING & FILTERING
• Masks secret data over the original
data by changing the luminance of
particular areas
• During masking, it embed the
message within significant bits of the
cover image
• Not susceptible to lossy techniques
because image manipulation does not
affect the secret message

9. Uses of MASKING & FILTERING
• Digital Watermarking – provides
identification pertaining to the owner;
i.e. license or copyright information
- Invisible vs Visible
• Fingerprinting – provides
identification of the user; used to
identify and track illegal use of
content

10. TRANSFORMATION
• Discrete cosine transformations
(DCT)
• Hiding in Frequency Domain

11. Uses of TRANSFORMATION
• Harder to implement
• More Robust against attack and
alteration
• Can be used in lossy compression
• Very Hard to detect as changes in
frequency domain are orders of
magnitude smaller than signal

12. Basics of Modern Steganography
fE: steganographic function "embedding"
fE-1: steganographic function "extracting"
cover: cover data in which emb will be hidden
emb: message to be hidden
key: parameter of fE
stego: cover data with the hidden message

13. DETECTING STEGANOGRAPHY ON
IMAGE
• Most Steganography algorithm are used LSB.
• Uses the Stastical Analysis on the LSB.
• Detect the secret data using the DCT method
while using the loosy format picture.

14. DRAWBACKS and RECOVER FROM
STEGANOGRAPHY IN IMAGE
• Do not uses loosy compression technique .
• Do not resize images.
• Do not convert to an image to another
format image.
• Do not change the luminance of an image.

15. SUMMARY
• 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 beneficial tool
for privacy

16. 1.http://en.wikipedia.org/wiki/Steganography
2.http://www.jjtc.com/stegdoc/index.html
3. C. Kurak, J. McHugh, "A Cautionary Note On
Image Downgrading," IEEE Eighth Annual Computer Security
Applications Conference, 1992.