Transcript
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.
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.