A Novel Steganographic Methodology For Secure Transmission Of Images

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					                                             (IJCSIS) International Journal of Computer Science and Information Security,
                                             Vol. 9, No. 5, May 2011

  A Novel Steganographic Methodology For
      Secure Transmission Of Images
                       Research ScholarAssociate ProfessorProfessor

                   *Department of Computer Science & Systems Engineering
                        AUCE(A), Andhra University,Visakhapatnam

Abstract :                                                  information which is to be embedded is called
        In recent days steganographictechniques             the stego message. Today steganography has got
have gained a lot of significance in many of the            many differentways to hide information like
security applications. In this paper a two layered          images,               audio,               video
secure methodology for transmitting multimedia              etc.Infactsteganography,cryptography,watermar
data is proposed and implemented. In the first              king are all different branches of information
layer,encoding based compression of the                     hiding.Information hiding also often termed as
message to be hidden is done based on                       data hiding or multimedia data hiding is a term
G delization and Alphabetic coding(AC). In the              covering a wide range of problems beyond
second layera steganographic approach is                    embedding messages in content. The term hiding
adopted for embedding of the encoded text into              can refer to either making the information
the cover image under frequency domain and the              perceptible or keeping the existence of
obtained stego image is transmitted securely                information secret. Compared with text or binary
using a novel encryption and decryption                     data, multimedia data often has high
methods.                                                    redundancy, large volumes and real-time
Keywords: Alphabetic Coding, Cover image,                   operations. All these properties require that
Encryption,        Decryption,G delization,stego            multimedia data should be compressed,
image.                                                      encrypted and securely transmitted for the
                                                            required applications. During the past decades,
             1. Introduction                                various multimedia encryption algorithms have
                                                            been proposed and studied.They can be
        Steganography is a modern and                       classified into three types which are image
dynamically developing part of information                  encryption, audio encryption, and video
security whichprotects information by its hiding            encryption. Generally, for different content,
techniques. Technically speaking, steganography             different encryption algorithms should be
is a covert communication technology, which                 adopted[1].In this paper a novel image encoding
allows secret information to be embedded into a             based on G delization[2],compression based on
cover/host message without significantly                    alphabetic coding[2],embedding the data into the
damaging the content of the cover message. The              cover image using a steganographic method
message usually will be an image and the secret             termed as middle band coefficient exchange

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                                                                                        ISSN 1947-5500
                                              (IJCSIS) International Journal of Computer Science and Information Security,
                                              Vol. 9, No. 5, May 2011

algorithm[3] and then secure transmission of the             spatial domain[4] where the intensity
data using a methodology based on encryption                 values(pixels) of the image are manipulated and
and decryption[4]are proposed and presented.                 data is hidden in the intensity values of the
                                                             images. The second method is frequency domain
                                                             where the frequency components of the digital
             2. Basic Concepts                               images are considered[5,6]. The secret data is
In this paper, the proposed methodology is                   embedded into the frequency components of the
divided intotwolayers(modules)for embedding                  image. It is observed that spatial domain
and securely transmitting the multimedia data.               manipulations are easy when compared to
The first layer consists of converting(encoding)             frequency domain, yet frequency domain
the secret image into string of Gödel Number                 provides more security when compared to
                                                             spatial domain techniques. So in this work,
Sequence throughGödelization, compressing the
                                                             frequency domain is chosen as the media and
encoded string using alphabetic coding                       discrete    cosine    transforms(DCT)[7]     are
andembedding the encoded compressed                          considered. After embedding the data into the
stringinto the cover image using middle band                 cover image, a key(k) and a stego image is
coefficient exchange method[3] under frequency               obtained which is given as input to the second
domain.In the second layer, encryption and                   layer. In the second layer, the obtained Key and
decryption techniquesare implemented for                     the stego image are encrypted and transmitted.
                                                             At the decoding end, the decoder decrypts the
secure transmission of the data. In this section a
                                                             stego image with his private key.
brief description of the definitions and the
concepts are presented.                                                3. Encryption and Decryption

         In the first layer, the secret image which                 With the continuing development of both
is to be transmitted securely is converted into              computer and Internet technology, multimedia
Gödel Number Sequence(GNS) through the                       data (images, videos, audios, etc.) is being used
concept of Gödelization[2]. According to it,the              more and more widely, in applications such as
intensity values at a point f(x,y) in the image are          video conferencing, broadcasting, education,
transformed into thepower of its primes.                     commerce, politics etc., and so the security
Consider a pixel value 39 which can be                       concerns are also increasing. To maintain
factorized as 31×131. So the Gödel number                    security, multimedia data should be protected
sequence of 39 = GN (0,1,0,0,0,1). The                       before transmission or distribution. The typical
sequence 0,1,0,0,0,1 can be encoded as 31×131                protection method is the encryption technique
as GN(0)= 2,GN(1)=3,GN(2)=5 and so on.After                  [9] which transforms the data from the original
converting each and every pixel into the                     form into an unintelligible form. Until now,
corresponding GNS, alphabetic compression                    various data encryption algorithms have been
technique(AC)[2] is applied to compress the                  proposed and widely used, such as AES, RSA,
GNS. According to AC, if the GNS has a                       or IDEA [9,10], most of which are used in text
sequence of more 0’s and 1’s, we represent 0’s               or binary data. It is difficult to use them directly
with ‘A’, 1’s with ‘B’, 2’s with ‘C’ and so on. If           in multimedia data, for multimedia data are
we encounter more than 3 same characters then,               often of high redundancy, of large volumes and
the number of occurrences are representedfirst               require real-time interactions, such as
followed by the character.After applying AC,                 displaying, cutting, copying, bit rate conversion,
there is a considerable amount of compression                etc. So in this paper, the multimedia data(the
achieved.The obtained encoded compressed                     secret image) is encoded and compressed using
string is embedded into the cover image using                Gödelization and alphabetic coding as explained
middle band coefficient exchange[2] method                   in the previous section.This encoded compressed
under frequency domain.According to literature               string is embedded into the cover image under
survey, embedding of secret data into the digital            frequency domain using middle band coefficient
images can be done in two domains. One is                    exchange method[10] to obtain a key and a stego

                                                       133                               http://sites.google.com/site/ijcsis/
                                                                                         ISSN 1947-5500
                                              (IJCSIS) International Journal of Computer Science and Information Security,
                                              Vol. 9, No. 5, May 2011

image. The key and stego image combined                      Number string(GNS) using Gödelization
together are encrypted and transmitted. At the               technique,later the encoded string is compressed
decoding end, it is decrypted using the decoder’s            using AC technique.This encoded compressed
private key. The encryption and decryption
                                                             string is embedded into the cover image using
models are shown below in fig 1 and 2
respectively.                                                middle band frequency exchange method in the
                                                             frequency domain.The output obtained after
                                                             embedding the data is a key and a stego
                                                             image.This provides the first layer of
Message                             Cipher                   security.The obtained key and the stego image is
                                                             now encrypted and decrypted.In this model,
(M)              Encryption         text                     MD5 is used for hashing,IDEA is used for the
                                                             encryption process. This provides second layer
                                                             of security and the data is transmitted. At the
                                                             decoder end the data is decrypted so as to obtain
                                                             themessage which is the key (k) and the image
                                                             data(M) which is obtained during embedding
                                                             under frequency domain.This data is decoded
                                                             with the key, then reverse Gödelization is used
Fig 1. Scheme for Encryption                                 to obtain GNS, upon which reverse alphabetic
                                                             coding is applied to obtain the image data
                                                             whichis reconstructed to obtain the secret image.
Here the stego image and the key generated
are given as input to the encryption
algorithm. The cipher text is given as input
to the decoder which decodes the cipher text
along with the receiver’s private key.The
decoding process is as shown below.                                                                                Encryption

Cipher text                           Messa                                Gödelization                                   ||
                                      ge(M)                                                    Stego image

                                                                    Gödel Number
                                                                    String (GNS)
Fig. 2Scheme for decryption                                                                                             Key
                                                                                                                       ( K)
          4. Proposed Methodology                                               coding(AC)

         The proposed methodology provides                         Encoded                        Embedder 
two layered security when compared to the                          string
traditional methods.The whole scheme of the
proposed methodology can be viewed as shown
below in figures3 and 4. The secret image(data)
which is to be hidden is encoded into Gödel

                                                       134                                   http://sites.google.com/site/ijcsis/
                                                                                             ISSN 1947-5500
                                                     (IJCSIS) International Journal of Computer Science and Information Security,
                                                     Vol. 9, No. 5, May 2011

   Fig 3. Scheme of proposed method at the
   encryption side

   The decryption side scenario is given below in
   fig 4.After decoding image can be reconstructed
   at the receiver’s side from the obtained data.

                                                                    Fig 4.Scheme of proposed method at the
                                                                    decryption side.
                 Algorithm (D)

                                                                    5. Results

                                                                    The proposed model is being implemented using
                                                                    Matlab 7.0 and JAVA. The results proved to be
                        K                                           more secure and satisfactory. Some test cases
                        M                                           are provided here.

                                                                    Sender’s side encryption:




                                           Reverse                  Receiver’s side decryption:
Reverse AC                                 Gödelization


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                                                                                                ISSN 1947-5500
                                               (IJCSIS) International Journal of Computer Science and Information Security,
                                               Vol. 9, No. 5, May 2011

                                                              that more data payload capacity can be achieved
                                                              which      sometimes        is   necessary        in    some

                                                              7. References:
                                                              [1] S. Lian, J. Sun, D. Zhang, and Z. Wang, “A
                                                              Selective Image Encryption Scheme Based on
                                                              JPEG2000Codec”,2004,Pacific-Rim Conference
                                                              on Multimedia (PCM2004), Lecture Notes in
                                                              Computer Science, Vol. 3332,pp 65–72.

                                                              [2]B.V.Rama       Devi,      P.PrapoornaRoja,
                                                              D.LalithaBhaskari,P.S.Avadhani,    “A    New
                                                              Encryption Method for Secure Transmission of
6.Conclusions& Future Work
                                                              Images”, 2010, International Journal of
Thus by implementing the proposed model it is                 Computer      Science     and     Engineering
                                                              (IJCSE),Vol.02,No.09, pp2801-2804.
observed that not only the data payload capacity
has increased but security is also enhanced when              [3]BNeil F. Johnson., Stefan C.Katzenbeisser,
compared     to    other    methods.By         using          “Chapter 3: A Survey of Steganographic
                                                              Techniques”, Arctech House, London, 2000.
G delization data is being encoded which is in
turn compressed so as to increase the data                    [4]P.S.Avadhani, D.LalithaBhaskari, “A Blind
payload capacity. This data is embedded into the              Scheme Watermarking Technique Using
                                                              GÖdelization Technique for RGB images under
cover image using middle band frequency                       spatial domain”, International Conference on i-
exchange methods under frequency domain                       warfare (ICIW-2010), Dayton,USA, 8th -9th
                                                              April 2010, pp 373-377.
which is proved to be secure.This data is again
transmitted using a novel encryption/decryption               [5]El-Gayyar,   Joachim   von     zurGathen,
                                                              “Watermarking Techniques Spatial Domain”,
model and data is retrieved at the decoder end. It            Digital Rights Seminar, University of Bonn,
is also observed that, after embedding the data               Germany, May 2006.
into the cover image there is no perceptual                   [6] D. Tzovaras, N. Karagiannis, M. G. Strintzis,
difference between the cover image and the                    “Robust image watermarking in the subband or
                                                              discrete cosine      transform domain”, 9th
stegoimage which satisfies the property of a                  European      Signal      ProcessingConference
blind steganographic scheme. In a blind scheme                (EUSIPCO’98), Greece, 8–11, Sept. 1998, pp
the cover image is not required at the decoder’s
end   and   the   implementation     results     are          [7]Bret    Dunbar,   “A    detailed     lookat
                                                              Steganographic Techniques and their use in an
satisfactory.As future enhancement, the same                  Open-Systems Environment”, The Information
technique can be enhanced for RGB images so                   Security Reading Room, SANS Institute, 2002.

                                                        136                               http://sites.google.com/site/ijcsis/
                                                                                          ISSN 1947-5500
                                       (IJCSIS) International Journal of Computer Science and Information Security,
                                       Vol. 9, No. 5, May 2011


[9]S. A. Vanstone, A. J. Menezes, and P. C.
Oorschot,   1996,“Handbook     of   Applied
Cryptography”,Boca Raton, FL: CRC Press.

[10]B.V.Rama Devi et.al., “ A New
Steganographic Algorithm for Image Hiding
using    GÖdelization   under    frequency
domain”,2011, IJARCS, Vol 2,No.2, pp 519-

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