Stegnography

STEGNOGRAPHYSTEGNOGRAPHY

What is StegnographyWhat is Stegnography The word stegnography is of Greek origin The word stegnography is of Greek origin

and means and means concealed writingconcealed writing from the from the greek word greek word stegnosstegnos means means coveredcovered or or protected and protected and grapheingraphein means means writingwriting..

It is a art of hiding the fact that It is a art of hiding the fact that communication is taking place by hiding communication is taking place by hiding info. in other info.info. in other info.

Mostly digital images are used because of Mostly digital images are used because of their frequency on the internet.their frequency on the internet.

Some KeywordsSome Keywords Cover imageCover image:: An image containing in An image containing in

embedded imageembedded image Cipher text:Cipher text: refers to encrypted data refers to encrypted data Cryptography:Cryptography: the art of protecting the art of protecting

information by encrypting it into an information by encrypting it into an unreadable format, called cipher text. A unreadable format, called cipher text. A secret key is used to decrypt the message secret key is used to decrypt the message plain text.plain text.

Plain text:Plain text: refers to any message that is refers to any message that is not encrypted.not encrypted.

Stego image:Stego image: It is result of applying some It is result of applying some stegnograpic processes to a plain text.stegnograpic processes to a plain text.

Lossless compression:Lossless compression: for most types for most types of data,lossless compression technique of data,lossless compression technique can reduce the space needed by about can reduce the space needed by about only 50%. No data lost in this process.only 50%. No data lost in this process.

Lossy compression:Lossy compression: It attempt to It attempt to eliminate unnecessary information.eliminate unnecessary information.

Least Significant Bit (LSB):Least Significant Bit (LSB): The bit The bit contributing the least value in a string of contributing the least value in a string of bits.bits.

Steganalysis:Steganalysis: The art of discovering The art of discovering and rendering useless convert messages.and rendering useless convert messages.

Stego image:Stego image: The result of combining The result of combining the cover image and embedded image.the cover image and embedded image.

HistoryHistoryDuring World War 2 invisible ink was used to write During World War 2 invisible ink was used to write information information on pieces of paper so that the paper appeared to the average person as just being blank pieces of paper. Liquids such as milk, vinegar and fruit juices were used, because when each one of these substances are heated they darken and become visible to the human eye.

In Ancient Greece they used to select messengers and shave their head, they would then write a message on their head. Once the message had been written the hair was allowed to grow back. After the hair grew back the messenger was sent to deliver the message, the recipient would shave off the messengers hair to see the secrete message.

Evolution Of StegnographyEvolution Of Stegnography

TechniquesTechniquesStegnography in TextStegnography in Text

Stegnography in AudioStegnography in Audio

Stegnography in VideoStegnography in Video

Stegnography in ImagesStegnography in Images

Image SteganographyImage Steganography : :

Images are used as the popular cover Images are used as the popular cover medium for steganography. A message is medium for steganography. A message is embedded in a digital image using an embedded in a digital image using an embedding algorithm, using the secret embedding algorithm, using the secret key. The resulting stego-image is send to key. The resulting stego-image is send to the receiver. On the other side, it is the receiver. On the other side, it is processed by the extraction algorithm processed by the extraction algorithm using the same key. During the using the same key. During the transmission of stego- image transmission of stego- image unauthenticated persons can only notice unauthenticated persons can only notice the transmission of an image but cant see the transmission of an image but cant see the existence of the hidden message. the existence of the hidden message.

Stegnography modelStegnography model

Cover image (C)Cover image (C)

Stego-key (K)Stego-key (K)

Message(M)Message(M) F(C,M,K) Stego-object(Z)

Bitmap Pictures and StegnographyBitmap Pictures and Stegnography

Bitmap Pictures(bmp) are the most Bitmap Pictures(bmp) are the most popular choices for stegnography.popular choices for stegnography.

JPEG,GIF formats are rarely used.JPEG,GIF formats are rarely used.

Software automatically converts other file Software automatically converts other file formats to formats to ““bmp”bmp” file formats. file formats.

BMP file formats is the simplest type of BMP file formats is the simplest type of pictures because it doesn’t have any pictures because it doesn’t have any technology for decreasing file size.technology for decreasing file size.

Bitmap image created from pixels that any Bitmap image created from pixels that any pixel created from three colors (RGB) each pixel created from three colors (RGB) each color of pixel has one byte info that show color of pixel has one byte info that show density of color.density of color.

Least Significant Bit in Least Significant Bit in StegnographyStegnography

Every byte is created from 8-bit that first is Every byte is created from 8-bit that first is Most Significant Bit(MSB) and last bit is Most Significant Bit(MSB) and last bit is Least Significant Bit(LSB).Least Significant Bit(LSB).We use LSB for writing our security We use LSB for writing our security information inside BMP pictures.information inside BMP pictures.We use 8We use 8thth layer of information , we should layer of information , we should change last bit of pixel,on other hand we change last bit of pixel,on other hand we have 3 bits in each pixel so we have have 3 bits in each pixel so we have

3*height*width3*height*width to write our information.to write our information.

Before writing our data must write name Before writing our data must write name of data (file), size.of data (file), size.

Using 3 pixel of picture to save a byte of Using 3 pixel of picture to save a byte of data.data.

EncryptionEncryption

Image fileImage file Information fileInformation file

BMP fileBMP file

DecryptionDecryption

Image fileImage fileInformation fileInformation file

BMP fileBMP file

Stegnography vs. CryptographyStegnography vs. CryptographySame purpose:Same purpose:

To hide/protect important informationTo hide/protect important information

Different approach:Different approach:

Stegnography:Stegnography: conceal information, making conceal information, making it unseenit unseen

Cryptography:Cryptography: encrypts information, making encrypts information, making it unreadableit unreadable

Crypto + Stegno =Crypto + Stegno = Added layer of Security Added layer of Security (one complements the other).(one complements the other).

AdvantagesAdvantages

It provide better security in LAN.It provide better security in LAN.Important files carrying confidential Important files carrying confidential information can be stored in server in information can be stored in server in encrypted form.encrypted form.Public key and private key can encrypt file.Public key and private key can encrypt file.No intruder can get any useful information No intruder can get any useful information from the original file during transmission.from the original file during transmission.It provide a better secured data storage It provide a better secured data storage and transmission both at the system level and transmission both at the system level and network level.and network level.

DisadvantagesDisadvantages

It provide the storing of data in It provide the storing of data in unprotected mode.unprotected mode.

Password leakage may occur and Password leakage may occur and leads to unauthorised access of data.leads to unauthorised access of data.

The intruder will affect stegos.The intruder will affect stegos.

Data Flow DiagramData Flow DiagramDFD Level 0

SOURCE

0.0

DESTINATIONPERSONAL

DATA

DFD Level 1

Encryption phase

Transmission Phase

Decryption Phase

Secret Data

0.0

1.0

2.0

3.0

DFD Level 2

INFORMATION FILE

IMAGEFILE

ENCRYPTION TRANSMISSION DECRYPTION

ENCRYPTIONALGORITHM

INFORMATION FILE

IMAGEFILE

DECRYPTION ALGORITHM

1.0 2.0 3.0

Waterfall modelWaterfall model

UML DiagramsUML DiagramsUse Case Diagram

Sequence Diagram

FutureFutureThe development of a system that will The development of a system that will utilize the Stegnographic Obliterator on utilize the Stegnographic Obliterator on incoming and email messages and incoming and email messages and attachments.attachments.Investigate the feasibility of embedding Investigate the feasibility of embedding the program in firewalls to act as a first the program in firewalls to act as a first line of defense against stegnographic data line of defense against stegnographic data transmission.transmission.Expand the stegnographic algorithm Expand the stegnographic algorithm attack method beyond LSB using some attack method beyond LSB using some other techniques.other techniques.