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Steganography
Ensuring
the confidentiality is one of the biggest challenges while transferring the
data. Various methods are used for providing security. One of the methods is
the steganography. The word steganography means concealed writing.
Steganography , the technique of hiding messages in other files for
transmission in a manner that an observer could not identify the occurrence of transmission,
is gaining popularity with current industry demands. It includes various
techniques of secret communications that veil the message. The various methods
include invisible inks, micro dots, character arrangement, digital signatures,
convert channels, least significant Bit insertion, Masking & Filtering and
spread-spectrum communications.
Thus
Steganography refers to the science of invisible
communication. Unlike cryptography, where the goal is to secure communications
from an eaves-dropper, steganographic techniques strive to hide the very
presence of the message itself from an observer. The general idea of hiding
some information in digital content has a wider class of applications that go
beyond steganography, the techniques
involved in such applications are collectively referred to as information hiding.
BASIC TYPES OF STEGANOGRAPHY
TEXT
Hiding information in text is
historically the most important method of steganography. An obvious method was
to hide a secret message in every nth letter of every word of a text
message. It is only since the beginning of the Internet and all the different digital file formats that is has
decreased in importance.
Text steganography using
digital files is not used very often since text files have a very small amount
of redundant data.Given the proliferation of digital images, especially on the
Internet, and given the large amount of redundant bits present in the digital representation of an image, images are
the most popular cover objects for steganography.
AUDIO/VIDEO
STEGANOGRAPHY
To
hide information in audio files similar techniques are used as for image files.
One different technique unique to audio steganography is masking, which
exploits the properties of the human ear to hide information unnoticeably. A
faint, but audible, sound becomes inaudible in the presence of another louder
audible sound.
This
property creates a channel in which to hide information. Although nearly equal
to images in steganographic potential, the larger size of meaningful audio
files makes them less popular to use than images.
IMAGE STEGANOGRAPHHY
Images are the most popular cover objects used for
steganography. In the domain of digital images many different image file
formats exist, most of them for specific applications. For these different
image file formats, different steganographic algorithms exist.
KEY
BASED STEGANOGRAPHY
On the basis
of keys used the types of Steganography are as follows:
1.
Pure Steganography
2.
Public key Steganography
3.
Private
key Steganography
These
categories convey the level of security with which the stego message is
embedded,transmitted and read.
1. Pure steganography
Pure
steganography uses no keypad system to embed clear text or ‘null cipher’ text
into the cover data in order to hide the existence of a secret message. It is
the least secure method. In steganalysis,this type is the easiest to crack
since once detected the message can only have been hidden in as many ways as
the number of steganographic algorithims which exists.
2. Public key
steganography
A
public key steganography allows two
parties,who have never met or exchanged a secret, to send hidden messages over
a public channel so that an adversary cannot even detect that these hidden
messages are being sent. In the more general case, two parties may wish to
communicate steganographically, without prior agreement on a secret key. In
this principle there are two keys,one being the public key which can be usually
obtained from public database and other a private key. Public key is used for
encryption and private key is used for decryption.
3.Private
key steganography
A
private key Steganography allows two
parties with a shared secret key to send hidden messages undetectatably over a
public channel. This technique can only
be used if the two parties communicating trust each other completely.
PRIVATE KEY STEGANOGRAPHY
BLOCK
DIAGRAM
The
block diagram of our project is as shown above. The data is to be sent by
hiding it into the cover image. A sender will first select the cover image in
which the secret data is to be hidden. Then according to his priorities he will
decide which algorithm to be used and finally the secret data will be embedded
in the cover image. This is called as Stego object. Both the original and stego
image are compared and if there is no visible difference then the stego image
will be sent to the receiver. The receiver should enter the decided key to start
the decryption phase. At the receiver side after entering the key the secret
data is extracted from the stego image.
IMAGE
STEGANOGRAPHY
Description:
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Image
definition
To
a computer, an image is a collection of numbers that constitute different light
intensities in different areas of the image. This numeric representation forms
a grid and the individual points are referred to as pixels.Most images on the
Internet consists of a rectangular map of the image’s pixels (represented as
bits) where each pixel is located and its colour. These pixels are displayed
horizontally row by row. The number of bits in a colour scheme, called the bit
depth, refers to the number of bits used for each pixel.
The smallest bit depth in current
colour schemes is 8, meaning that there are 8 bits used to describe the colour
of each pixel. Monochrome and greyscale images use 8 bits for each pixel and
are able to display 256 different colours or shades of grey. Digital colour
images are typically stored in 24-bit files and use the RGB colour model, also
known as true colour . All colour variations for the pixels of a 24-bit image
are derived from three primary colours: red, green and blue, and each primary
colour is represented by 8 bits.
Thus in one given pixel, there can
be 256 different quantities of red, green and blue, adding up to more than
16-million combinations, resulting in more than 16-million colours. Not
surprisingly the larger amount of colours that can be displayed, the larger the
file size.
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