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International Journal of Engineering Trends and Technology (IJETT) – Volume 11 Number 8 - May 2014
ISSN: 2231-5381 http://www.ijettjournal.org Page 388
A Survey on various types of Steganography and
Analysis of Hiding Techniques
Navneet Kaur#1, Sunny Behal#2
1Research Scholar, Department of Computer science Engineering, SBSSTC, India
2Associate Professor, Department of Computer science Engineering, SBSSTC, India
Abstract—Digital Steganography is the science that involves
communicating secret data in an appropriate multimedia carrier,
e.g., image, audio, and video files. Under this assumption, if the
feature is visible, the point of attack is evident, thus the here goal
is conceal to the existence of the embedded data .This is totally
review paper, in which we provide the comparison of available
steganography technology hiding text in an image file using Least
Significant Bit (LSB) based Steganography, Discrete Cosine
Transform (DCT) based Steganography and Discrete Wavelet
Transform (DWT) based steganography. The LSB algorithm is
implemented in spatial domain in which the payload bits are
embedded into the least significant bits of cover image to derive
the stego-image whereas DCT & DWT algorithm are
implemented in frequency domain in which the stego -image is
transformed from spatial domain to the frequency domain.
Keywords—Steganography, Cryptography, Least Significant Bit
(LSB); Discrete Cosine Transform (DCT); Discrete Wavelet
Transform (DWT).
I. INTRODUCTION
Steganography is the art and science of covered writing (hide
in plain sight) and its techniques are in use from hundreds of
years. Digital Steganography is the technique of securing
digitized data by hiding it into another piece of data. Today,
in digital age the easy access to any form of data such as audio,
videos, images and text make it vulnerable to many threats [1].
The data can be copied for purpose of copyright violation,
tampered with or illegally accessed without the knowledge of
owner. Therefore, the need of hiding secret identification
inside different types of digital data is required such that
owner can prove copyright ownership; identify attempts to
tamper with sensitive data and to embed annotations. The
main task of the field of steganography is the storing, hiding,
and embedding of secret data in all types of digital data. The
main goal of steganography is to communicate securely in a
completely undetectable manner [2] such that no one can
suspect that it exist some secret information. Unlike
cryptography, which secures data by transforming it into
another unreadable format, steganography makes data
invisible by hiding (or embedding) them in another piece of
data [3]. Thus cryptography is science of overt secret
writing while steganography as covert secret writing. The
cover, host or the carrier is the target media in which
information is hidden so that other person will not notice the
presence of the information. The modified cover, including
the hidden data, is referred to as a stego object which can be
stored or transmitted as a message [4]. The secret information
can be embedded in various types of covers. If
information is embedded in a cover text (text file), the
result is a stego-text object. Similarly, it is possible to
have cover audio, video and image for embedding
which result in stego-audio, stego-video and stego-
image respectively. Nowadays, the combinations of
steganography and cryptography methods are used to ensure
data confidentiality [5] and to improve information security.
Steganography is used in other grounds also like copy right,
preventing e-document forging. Table 1 shows the comparison
of various secret communication techniques used nowadays
TABLE I
COMPARISON OF SECRET COMMUNICATION TECHNIQUES
Secret
Communication
Techniques Confidentiality Integrity Un-
removability
Encryption
Yes
No
Yes
Digital
Signatures
No Yes/No
No
Steganography
Ye
s/No
Yes/No
Yes
The proposed paper provide a systematic survey of existing
Steganography research by categorizing existing methods
according to the certain features and analysing the advantages
of these features. The motive of the paper is to provide
researchers with in-depth study of subject. The proposed
paper is organized in 4 sections. Section 2 deals with the
classification of various types of steganography. The section 3
demonstrates the comparative study of existing steganography
methods.
Fig1. Process of steganography
International Journal of Engineering Trends and Technology (IJETT) – Volume 11 Number 8 - May 2014
ISSN: 2231-5381 http://www.ijettjournal.org Page 389
Figure 1 shows a simple representation of the generic
embedding and decoding process in steganography. In this
example, a secret image is being embedded inside a cover
image to produce the stego image. The first step in embedding
and hiding information is to pass both the secret message and
the cover message into the encoder. Inside the encoder, one or
several protocols will be implemented to embed the secret
information into the cover message. The type of protocol will
depend on what information you are trying to embed and what
you are embedding it in. For example, you will use an image
protocol to embed information inside images
II. CLASSIFICATIONS OF DIGITAL STEGANOGRAPHY
The steganography can be classified according to its
importance and goals. So; various types of steganography are:
Fig2. Types of steganography
1) Linguistic Steganography:
Linguistic technique is used to hide the message within the
cover text in non-obvious way such that the presence of
message is imperceptible to an outsider [6]. It is divided into
two types:
A) Semagrams: It uses only symbols and signs to hide the
information. It is further categorized into two ways:
i) Visual Semagrams: A visual semagrams uses physical
objects used every day to convey a message. For example: the
positioning of items on a particular website.
ii)Text Semagrams: This type is used to hides a message by
modify the appearance of the carrier text, or by changing font
size and type, or by adding extra space between words and by
using different flourished in letters or handwritten text.
B) Open Code: In this approach the message is embedded in
legitimate paraphrases of cover text in the way such that it
appears not obvious to an unsuspecting observer. It can be
achieved by two ways viz., Jargon which is understood only
by a group of peoples and Cipher which uses some concealed
ciphers to hide a message openly in the carrier medium. A
subset of jargon codes are cue codes, where certain pre-
arranged phrases convey meaning.
2) Technical Steganography:
Technical steganography uses special tools, devices or
scientific methods to hide a message. In this type one can use
invisible ink, microdots, computer based methods or various
hiding places to keep message secret
I) Cover: The cover message is the carrier of the message such
as image, video, audio, text, or some other digital media [7].
The cover is divided into blocks and message bits which are
hidden in each block. The information is encoded by changing
various properties of cover image. The cover blocks remain
unchanged if message block is zero [8].
A) Text Steganography: In this approach the cover text is
produced by generating random character sequences,
changing words within a text, using context-free grammers or
by changing the formatting of an existing text to conceal the
message. The cover text generated by this approach can
qualify for linguistic steganography if text is linguistically-
driven. Although these text- based methods has its own
unique characteristics for cover text but suffers from various
problems from both a linguistic and security stand point [9]
[10].
B) Image Steganography:
This Steganography technique is more popular in recent year
than other steganography possibly because of the flood of
electronic image information available with the advent of
digital cameras and high-speed internet distribution. It can
involve hiding information in the naturally occurred noise
within the image. Most kinds of information contain some
kind of noise. Noise refers to the imperfections inherent in the
process of rendering an analog picture as a digital image. In
Image steganography we can hide message in pixels of an
image. An image steganographic scheme is one kind of
steganographic systems, where the secret message is hidden in
a digital image with some hiding method [11]. Someone can
then use a proper decoding procedure to recover the hidden
message from the image. The original image is called a cover
image in steganography, and the message-embedded image is
called a stego image [12] [13]. Various methods of image
steganography are:
i) Data Hiding Method: hiding the data, a username and
password are required prior to use the system. Once the user
has been login into the system, the user can use the
information (data) together with the secret key to hide the data
inside the chosen image. This method is used to hiding the
International Journal of Engineering Trends and Technology (IJETT) – Volume 11 Number 8 - May 2014
ISSN: 2231-5381 http://www.ijettjournal.org Page 390
existence of a message by hiding information into various
carriers. This prevents the detection of hidden information
[14].
ii) Data Embedding Method: For retrieving the data, a secret
key is required to retrieving back the data that have been
embedded inside the image. Without the secret key, the data
cannot be retrieved from the image. This is to ensure the
integrity and confidentiality of the data. The process of
embedding the message inside the image, a secret key is
needed for retrieving the message back from the image, the
secret message that is extracted from the system is transfer
into text file and then the text file is compressed into the zip
file and zip text file is converting it into the binary codes [15].
iii) Data Extracting Method: It is used to retrieve an original
message from the image; a secret key is needed for the
verification. And for extracting method, a secret key is needed
to check the key is correct with the decodes from the series of
binary code. If key is matched, the process continues by
forming the binary code to a zipped text file, the unzip the text
file and transfer the secret message from the text file to
retrieve the original secret message [15].
I) Features Of Image Steganography:
1) Transparency: The steganography should not affect the
quality of the original image after steganography.
2) Robustness: Steganography could be removed intentionally
or unintentionally by simple image processing operations like
contrast or enhancement brightest gamma correction,
steganography should be robust against variety of such attacks.
3) Data payload or capacity: This property describes how
much data should be embedded as a steganography to
successfully detect during extraction.
C) Audio Steganography:
Audio steganography, the hiding of messages in audio “noise”
(and in frequencies which humans can’t hear), is another area
of information hiding that relies on using an existing source as
a space in which to hide information. Audio steganography
can be problematic and can be useful for transmitting covert
information in an innocuous cover audio signal [8] [16]
A) Types of Audio Steganography:
1) Echo Hiding
2) Phase Coding
3) Parity Coding
4) Spread Spectrum
5) Tone insertion
1) Echo Hiding: This method embeds data or text into audio
signals by adding a small echo to the host signal. The Nature
of the echo is a resonance added to the host audio. Then the
data is invisible by varying three echo parameters: initial
amplitude, decay rate, and offset. If only one echo is produced
from the original signal, then only one bit of information
could be encoded [17]
2) Phase Coding: One of the most effective coding methods in
terms of the signal-to perceived noise ratio. In this phase
components of sound are not as perceptible to the human ear
as noise is. It can be done by substituting the phase of an
initial audio segment with a reference phase that represents
the data. It encodes the message bits as phase shifts in the
phase spectrum of a digital signal, achieving an inaudible
encoding in terms of signal-to-perceived noise ratio
subsequent segments is then adjusted store the relative phase
between segments. Disadvantage: It is a complex method and
has low data transmission rate [17] [18]
3) Parity Coding: This method breaks a signal down into
different regions of samples and encodes each bit from the
secret message in a sample region's parity bit. If the parity bit
of selected region does not match the secret bit to be encoded,
Disadvantage: This method like LSB coding is not robust in
nature. Advantage: The sender has more of a choice in
encoding the secret bit, and the signal can be changed in a
more unobtrusive manner [17]
4) Spread Spectrum: This is analogous to a system using an
implementation of the LSB coding that randomly spreads the
message bits over the entire sound file. It is used to encode a
category of information by spreading the encoded data across
frequency spectrum. This allows the signal reception, even if
there is interference on some frequencies. Disadvantage: It
can introduce noise into a sound file [17] [18].
5) Tone insertion: In this inaudibility of lower power tones in
the presence of significantly higher ones. Tone insertion
method can resist to attacks such as low-pass filtering and bit
truncation addition to low embedding capacity, embedded
data could be maliciously extracted since inserted [19]
A) Uses of Audio Steganography:
1) Audio data hiding can be used anytime you want to
hide data. There are many reasons to hide data but most
important is to prevent unauthorized persons from becoming
aware of the existence of a message.
2) Audio data hiding can also be used in the non
commercial sector to hide information that someone wants to
keep private.
3) It can also be used in forensic applications for inserting
hidden data into audio files for the authentication of spoken
words and other sounds
International Journal of Engineering Trends and Technology (IJETT) – Volume 11 Number 8 - May 2014
ISSN: 2231-5381 http://www.ijettjournal.org Page 391
III) TECHNIQUES OF STEGANOGRAPHY:
1) Method: In spatial domain, images are represented by
pixels. Simple watermarks could be embedded by modifying
the pixel values or the least significant bit (LSB) values [20].
It directly loads the raw data into the image pixels. Some of its
algorithms are LSB, SSM Modulation based technique.
A)Spatial Domain: In this technique only the least significant
bits of the cover object is replaced without modifying the
complete cover object. It is a simplest method for data hiding
but it is very weak in resisting even simple attacks such as
compression, transforms [23].
i) Least Significant Bit (LSB):
This is the most common, simple approach for embedding
data in a cover image. The least significant bit (8th bit) of one
or all of the bytes inside an image is changed to a bit of the
secret message. When we use 24-bit image, three color bits
components are used which are red, green, blue, each byte
store 3 bits in every pixel. An 800 × 600 pixel image, can thus
store a total amount of 1,440,000 bits or 180,000 bytes of
embedded data. For example a grid for 3 pixels of a 24-bit
image can be as follows:
(00101101 00011100 11011100)
(10100110 11000100 00001100)
(11010010 10101101 01100011)
When the number 200, which binary representation is
11001000, is embedded into the least significant bits of this
part of the image, the resulting grid is as follows:
(00101101 00011101 11011100)
(10100110 11000101 00001100)
(11010010 10101100 01100011)
The number was embedded into the first 8 bytes of the grid,
only the 3 underlined bits needed to be changed according to
the embedded message. On average, only half of the bits in an
image will modified to hide a secret message using the
maximum cover size. Since there are 256 possible intensities
of each primary color, changing the LSB of a pixel results in
small changes in the intensity of the colors. These changes
cannot be visible by the human eye due to the message hidden.
In these consecutive bytes of the image data – from the first
byte to the end of the message – are used to embed the
information. And easy to detect, more secure system for the
sender and receiver to share a secret key that specifies only
some pixels to be changed In its simplest form, LSB makes
use of BMP images, since they use lossless compression. It
hide a secret message inside a BMP file, one would require a
very large cover image. In BMP images of 800 × 600
Pixels are not often used on the Internet and might arouse
suspicion. For this reason, LSB steganography has also been
developed for use with other image file formats [4]. It is a
simple method for embedding data in a cover image. This is
the simplest algorithm in which information can be inserted
into every bit of image information. Given an image with
pixels, and each pixel being represented by an 8-bit sequence,
the watermarks are embedded in the last (least significant bit)
of selected pixels of the image proposed a simple data hiding
technique by simple LSB substitution. In this technique last
bit of host data is randomly changed and produce the
watermarked data at output. The cover LSB media data are
used to hide the message [21].
ii) Pixel Value Differencing:
It provides both high embed-ding capacity and outstanding
imperceptibility for the stego-image; this segments the cover
image into non overlapping [8] blocks containing two
connecting pixels and it modifies the pixel difference in each
pair for data embedding.
iii) Pixel Indicator:
This method gives the stego images of better quality than the
traditional method while maintaining a high embedding
capacity and it also uses concept of hiding the data using the
difference between the pixel values [20]. It’s more complex
way of hiding information in an image. Transformations are
used on the image to hide information in. Transform domain
embedding can be termed as a domain of embedding
techniques in frequency domain; image is represented in terms
of its frequencies.
B) Frequency Domain:
i) Discrete Cosine Transformation:
These methods convert the uncompressed image into JPEG
compressed type[22]It is based on data hiding used in the
JPEG compression algorithm to transform successive 8x8-
pixel blocks of the image from spatial domain to 64 DCT
coefficients each in frequency domain. [23]The main
advantage of this method is its ability to minimize the block
like appearance resulting when boundaries between the 8x8
sub-images become visible (known as blocking artefact).
ii) Discrete Wavelet Transformation:
It gives the best result of image transformation .it splits the
signal into set of basic functions .there are two types of
wavelet transformation one is continuous and other is discrete
[24] This is the new idea in the application of wavelets, in this
the information is stored in the wavelet coefficients of an
image, instead of changing bits of the actual pixels. It also
performs local analysis and multi-resolution analysis. DWT
transforms the object in wavelet domain and then processes
the coefficients and performs inverse wavelet transform to
show the original format of the stego object [25].
International Journal of Engineering Trends and Technology (IJETT) – Volume 11 Number 8 - May 2014
ISSN: 2231-5381 http://www.ijettjournal.org Page 392
IV COMPARISON OF DIFFERENT STEGANOGRAPHIC
TECHNIQUES TABLE 2:
Steganogra
phy
Techniques
Cover
Media
Embedding
Techniques
Advantages
Image
Hiding
Image
1.LSB(Lea
st
Significant
Bit)
This method is used
the least significant
bit of every pixel in
one image to hide
the most significant
bit of another
Simplest & easiest
way of hiding
information
2.DCT
(Discrete
Cosine
Transform)
Embeds the
information by
altering the
transformed DCT
co-efficient
Hide data can be
distributed more
evenly over the
whole image in
such a way to
make it robust
3.DWT
(Discrete
Wavelet
transform)
This technique work
by talking many
wavelet to encode a
whole image
Coefficient of
wavelet are altered
with the noise
within tolerable
level
III. CONCLUSION
In this paper provides literature review on digital
steganography. As steganography becomes widely used in
computing, there are issues that need to be resolved. There are
a wide variety of different techniques with their own
advantages and disadvantages. We surveyed various types of
steganography. We studied the various techniques, Least
Significant Bit (LSB), DCT (Direct Cosine Transform), DWT
(Discrete Wavelet Transform)which helps to improve in
security.
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