Steganography

STEGANOGRAPHY

AGENDA Etymology What Is Steganography? History Evolution Live Cyber Case Study Some Terminologies Of Steganography Basic Principle in Steganography Live Demonstration Steganography Vs Crptography Steganography Tools Steganalysis Conclusion References

STEGANOGRAPHY

Etymology:

The word steganos means "covered or protected", and graphy means "writing“. Thus steganography means "concealed writing".

WHAT IS STEGANOGRAPHY?

Steganography is the art and science of hiding a message in a medium, such as a digital picture or audio file, so as to defy detection.

Messages are hidden in such a way that no one, apart from the sender and intended recipient, suspects the existence of the message.

CONTD.. For an example, a message might be hidden within an image

by changing the least significant bits to be the message bits.

EVOLUTION

Cryptography

Steganography

Watermarking

STEGANOGRAPHY

History:

Greek history – warning of invasion by scrawling it on the wood underneath a wax tablet. To casual observers, the tablet appeared blank.

Both Axis and Allied spies during World War II used such measures as invisible inks -- using milk, fruit juice or urine which darken when heated.

Invisible Ink is also a form of Steganography.

LIVE CYBER CASE STUDY

SOME TERMINOLOGIES

Cover medium (Example-Image)

Embedded message (Message to be hidden)

Stego-key (Key to extract hidden message)

Stego-Object (Seen by casual observer)

Therefore,

Cover-medium + embedded-message = stego-object

BASIC PRINCIPLE IN STEGANOGRAPHY

Encoder

Decoder

Secret MsgCover Image

Stego Object

Original Image

Secret Msg

Communication Channel

Key

LIVE DEMONSTRATION

CONTD…

STEGANOGRAPHY CARRIER FILES

Jpeg Bmp Gif Audio

Wav MP3

Other Types

+

STEGANOGRAPHY TOOLS

• Steganos• S-Tools • StegHide • Invisible Secrets • JPHide• Camouflage• Hiderman• Many others…

STEGANOGRAPHY VS CRYPTOGRAPHY

Steganography(hide existence of the secret

message, but do not use encryption)

Cryptography(encrypt the message,but do

not hide the message)

• Ideally nobody can see both parties are secretly communicating.

• Innocent.

• Anybody can see both parties are communicating in secret.

• Suspicious.

STEGANALYSIS

Identification of hidden files :

•Identifying the existence of a message.

•Not extracting the message.

•Technically, Steganography deals with the concealment of a message, not the encryption of it.

•Steganalysis essentially deals with the detection of hidden content.

•How is this meaningful???

HOW TO IDENTIFY? By identifying the existence of a hidden message, perhaps we

can identify the tools used to hide it.

If we identify the tool, perhaps we can use that tool to extract the original message.

STEGANALYSIS:METHODS OF DETECTION

• Visual Detection (JPEG, BMP, GIF, etc.)• Audible Detection (WAV, MPEG, etc.)• Statistical Detection (changes in patterns of the pixels

or LSB – Least Significant Bit) or Histogram Analysis• Structural Detection - View file properties/contents• Size difference• Date/time difference• Contents – modifications• Checksum

ANOMALY – VISUAL DETECTION

Detecting steganography by just viewing the Stego-object.

Can you see any difference between the two??

ANOMALY – KURTOSIS

Kurtosis The degree of flatness and peakedness of

describing a frequency distribution: Random house dictionary.

ANOMALY – HISTOGRAM ANALYSIS

Histogram analysis can be used to identify a file with a hidden message.

Histogram of Original file.

CONTD…

Histogram of file with embedded message.

Here it can be seen that this histogram has a noticeable repetitive trend unlike the original one.

ANOMALY ANALYSIS - COMPARE FILE PROPERTIES

• Compare the properties of the files• Checksum• C:\GNUTools>cksum a:\before\helmetprototype.jpg

3241690497 240759 a:\before\helmetprototype.jpg• C:\GNUTools>cksum a:\after\helmetprototype.jpg

3749290633 235750 a:\after\helmetprototype.jpg

• Properties 04/04/2003 05:25p 240,759 helmetprototype.jpg 04/04/2003 05:26p 235,750 helmetprototype.jpg

COMPARE THE PROPERTIES OF THE FILESCHECKSUM

C:\GNUTOOLS>CKSUM A:\BEFORE\HELMETPROTOTYPE.JPG3241690497 240759 A:\BEFORE\HELMETPROTOTYPE.JPGC:\GNUTOOLS>CKSUM A:\AFTER\HELMETPROTOTYPE.JPG3749290633 235750 A:\AFTER\HELMETPROTOTYPE.JPG

PROPERTIES04/04/2003 05:25P 240,759 HELMETPROTOTYPE.JPG04/04/2003 05:26P 235,750 HELMETPROTOTYPE.JPG

FILE EXTENSION:

Hex Signature File Extension ASCII Signature

SUMMERY Steganography is used for data hiding to provide security to

confidential infromation. Its a technique which is used to hide the message within

some medium. To further improve the security of the secret message in the

cover image, we have used encryption to encrypt the secret message before it is embedded.

While Steganography deals with hiding the message, Steganalysis deals with identifying the existence of any hidden message within file.

Using steganalysis if we identify the existence of any hidden message then we can easily identify how to extract it.

REFERENCES: Wikipedia

http://en.wikipedia.org/wiki/Steganography StrangeHorizons

http://strangehorizons.com/steganography.shtml TIFR

http://www.tifr.res.in/~sanyal/papers/Soumyendu_Steganography_Steganalysis_different_approaches.html

QUERIES