Steganoghraphy

SELF STUDY SEMINAR

SteganographyBy

ABTRACT

To learn and understand what Steganography is and

about its importance.

How Steganography works.

Steganographic Methodologies to achieve Covert

Communications.

Techniques to detect the use of Steganography.

Comparison with other famous methodology of securing

data like Cryptology.

INTRODUCTION

What exactly is Steganography?

“Steganography” “Covered or Hidden Writing”

The art &science of communicating in a way which

hides the existence of the communication.

Boosts the Concept of Information hiding without altering

or recasting the Information.

Practiced in data hiding in digital files like document files, multimedia files and even protocols.

Importance:

Primary Goal is to hide messages inside other harmless messages.

Doesn’t allow any other person to detect a secrete message is

being passed.

Required by an individual as well as Governments and

organizations.

Protects Intellectual Property Rights of Copyright Owners done via

Watermarking.

The Basic Steganographic Model

Any Steganographic

Methodology will follow the same

model using following :

Carrier Media

Encoding

process/Steganographic

Algorithm

Payload

Unique Key

Stego-Media

The Recovering Process

Steganography In Text Files

Text Steganography is the trickiest due to the deficiency of

redundant information . However the are some methods to achieve it:

Line Shift Coding

Vertical shifting of text line position to hide data.

Word Shift Coding

Horizontal shifting of words

Feature Coding

Alteration of one or more features of the text.

Steganography in Audio Files

Changing of Individual bits that make up the digital

Audio file.

A precise control allows the changes to be made to the

binary sequence which are not discernible to human

ears.

Some of pre-established and effective methods are:

Steganography in Audio Files

Least Significant Bit Coding

Replaces the least

significant bit in some

bytes of the cover file to

hide a sequence of byte

containing the hidden

data.

Doesn’t cause quality

degradation.

Steganography in Audio Files

Least Significant Bit Coding

Echo Hiding

Introduces Echoes into

discrete signals.

Each block of signal holds

one bit data.

Steganography in Audio Files

Least Significant Bit Coding

Echo Coding

Phase Coding

Replacing the phase of an initial audio segment with

a reference phase to represent data.

Steganography in Images

8-bit or higher color mages are more preferable than other images.

In these images each pixel is represented as a single byte, with

pixel value of 0-255.

Recommended Images are ones using 256 shades of grey as

Palette.

Shades change very gradually between pixel value.

Images having large area of solid color should be avoided.

Steganography in Images

Insertion Technique

The LSB of the cover image are altered.

Pixels: (00100111 11101001 11001000)

(00100111 11001000 11101001)

(11001000 00100111 11101001)

The Code for letter ‘A’ which is to be hidden: 10000001

After the Insertion technique:

Resultant Pixels: (00100111 11101000 11001000)

(00100110 11001000 11101000)

(11001000 00100111 11101001)

Steganography over Networks

Methods to implement Steganography over a network are:

Hiding in an attachment

Hiding in a Transmission

Hiding in Overt Protocol

Data Camouflaging

You take data, put it in normal network traffic, and

modify the data in such a way it looks like a overt

protocol.

Making a text file like a HTML file.

Covert Channels

Communications paths not designed for transferring

information.

But these are used for covert communications.

TCP/IP Headers.

In IP header, the IP identification number field can be

changed as the protocols keeps working properly.

In the TCP headers, the sequence and

acknowledgement number fields are used to hide data.

Steganalysis

Steganography also poses threat.

Misuse by anti-social elements to send messages without

being detected.

There is a need to Detect Stego-Media.

Steganalysis is the study of detecting messages hidden

using steganography.

The goal of Steganalysis is to identify suspected

packages, determine whether or not they have a

payload encoded into them, and, if possible, recover

that payload.

Steganalysis

Correlation Technique:

A set of unmodified files from same source are inspected with

message file for various statistics.

The unmodified carrier and the message files are compared in

respect of these statistics.

If the message file is indeed a Stego-File, the differences will be

seen in the statistics as payload encoded into the file causes

these differences.

However not every time the unmodified carrier is available.

Steganalysis

Randomness Technique:

Using concept of randomness.

A unmodified carrier will have

no randomness, so its histogram

shows peaks & valleys

A stego-file will have randomness and its histogram

shows flatness.

There is no need for a

unmodified carrier to detect

stego-files.

Applications of Steganography

Digital Watermarking:

A Digital Watermark is a marker embedded in a noise tolerant multimedia file.

Uses Steganography techniques to embed data into the carrier media, with one

exception.

Aims for the robustness of the payload(watermark), even if it results in being

visible or noticeable.

Can be embedded as long as carrier media doesn’t get distorted.

Digital watermarking helps in

Copyright Protection

Source tracking

Distribution Monitoring

Authentication of Media

Tamper Proofing

To counter the risk of a files being transmitted to be tampered or altered to false

information.

Just like a Watermark, data can be embedded onto the carrier as a check for tampering.

If the file undergoes some tampering, the embedded data will reflect the

changes also.

Removal of the embedded data is also not a option as the removal will result in

the destruction of the carrier file itself.

In Modern Printers:

Printers use Steganographic

techniques to embed information

about the document being printed

in every print.

In Biometrics:

Avoid unauthorized use of

genetically engineered material.

Hiding secrete messages in DNA

sequences for identification.

Steganography

Only Sender & Receiver knows the existence of the message.

Prevents Discovery of the very existence of Communications.

Does not Alter the structure & content of the message.

Cryptography

The Existence of Message is Known to all..

Prevents Unauthorized party to discover the contents of

Communications.

Alters the structure of the Message.

Steganography is more Advantageous!

vs.

Future of Steganography

Improved Resistance to Analysis

Presently, Stego-Media are more prone to be detected.

Once detected, it will be easy to extract the hidden message.

Making Stegos undetectable, irretrievable for those not intended

to.

Higher Encoding Density

Ability to hide more amount of data.

Presently encoding density is limited without degrading the

carrier.

CONCLUSION Steganography is interesting subject, different than Cryptology and

System Administration.

Based on the dilemma “YOU NEVER KNOW IF A MESSAGE IS HIDDEN”.

Not only limited to Data Hiding, but can be put to a more Versatile use.

Both Steganography and Cryptography together can achieve Data Hiding.

Expectation of more advancement in technology & efficiency

While keeping a check on its illicit use by others.