1 - Acta Technica Corviniensis

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converting the data also increases the complexity byapplying the complementary rules and then indexingthe garbled sequence. The second step involves theextraction of the hidden data from the DNA sequencewhere in exactly a reverse operation is performed tothe first step.COMPARATIVE ANALYSIS OF VARIOUS DATA HIDINGTECHNIQUESIn this section a comparative analysis of different datahiding schemes in steganography is presented.The authors in [6], [7], [13], [14] and [16] have allpresented techniques to hide data in the still imagesand generated stego‐images as the output. In [6] theauthors embed the data in RGB 24 bit color image byusing the linked data structures where in, the datahidden in the image is linked with other data.The advantage of this method is that hiding the datarandomly than sequential will make it difficult for theattacker to locate it and also without theauthentication key the attacker will not be able toaccess the next piece of data in the image. Instead ofusing the whole image as the cover image, the authorsin [7] have proposed a method that segments theimage into blocks of equal sizes. Also, the processinvolved in this method is reversible hence there is noloss of hidden data. The approach followed in thisscheme to conceal data is quite different. In thistechnique the histograms of the blocks of images istaken and they are shifted to minimum point of thehistogram and then the data is hidden between thesepoints. The improvement of this technique is that itprovides higher capacity to hide data than theprevious method.In [13] optimized bit plane splicing method isimplemented. In this method the intensity value of thepixel is divided into different planes and rather thanusing the traditional method of hiding the data intoLSB of the pixel and plane by plane, the data in thisapproach is hidden based on the intensity of thepixels. The pixels are grouped based on the intensityand then number of pixels used to represent the datais chosen depending on the intensities. Also, ratherthan hiding the data sequentially in the planes, thedata is hidden randomly and during the transmissionof the data the planes are transferred randomly tomake it difficult to intercept the data. The advantageof this technique is that by grouping the pixelsaccording to the intensity more number of bits isavailable to represent the hidden data than just theLSB of the pixel. In [16] to increase and utilize thehigher bit planes to hide the data a different approachfrom the one discussed earlier is employed. This isachieved by converting the original bit planes intosome other binary number system using the primeACTA TECHNICA CORVINIENSIS – Bulletin of Engineeringnumbers as the weighted function. This enables to usemore number of bits to represent the hidden data.The authors in [17] and [19] use audio signals as thecover media to hide the sensitive data. In [17] theauthors present two techniques to hide data in theaudio signals. In the first method before hiding thedata in the LSB of the sample of the audio signal theparity of the sample checked. This method makes theattacker difficult to guess the transmitted data. In thesecond approach, the LSB’s are XOR’ed and dependingon the result of this operation and the hidden data theLSB of the sample data is decided to be changed orleft unchanged. In [19] a separate approach isfollowed where in the stereo audio signals are used toembed the data. In the proposed algorithm thepolarity of reverberations is applied to the highfrequency signals which are then replaced by onemiddle channel to embed the critical data.Jigsaw‐based approach [20] is used to transfer dataover the communication channel securely. In thisscheme the data is fragmented in block of variablesizes and a message authentication code (MAC) is usedto authenticate each and every piece of data. Also,every message is prefixed and suffixed with a binary 1along with XOR‐ing the data with the randomlygenerated one‐time pad.By fragmenting the data theattacker is unable to make sense of the data at thesame time he cannot access the data unless he possessthe authentication code for the data. A diverseapproach is followed by the authors in [21]. In thisscheme the redundant fields in the IPv4 header isexploited to mask the data. The fragment bit of FLAGSand the 16‐bit identification fields are utilized to passthe delicate data over the communication network.TABLE I below provides a brief summary of the datahiding techniques in steganography with theiradvantages.CONCLUSIONSIn this paper we discussed about steganography andpresented some notable differences betweensteganography and cryptography. We also surveyedvarious data hiding techniques in steganography andprovided a comparative analysis of these techniques.In the Introduction section we discussed about varioussecurity flaws and vulnerabilities in internet.We also discussed about various techniques to enablethe secure transfer of data with the help of methodslike cryptography, steganography, hashing, andauthentication. In the next section we presentedvarious techniques to conceal data in steganography.Comparative Analysis has been presented in Section 3,followed by the Conclusion.382012. Fascicule 3 [July–September]
ACTA TECHNICA CORVINIENSIS – Bulletin of EngineeringTable Ia: A brief summary of various data hidingtechniques in steganography ‐ Data HidingTechniques ProposedCover Media1. StillImage2. AudioSignal3. IPv4HeaderData Hiding Techniques Proposed1. In [6] the authors implementeda scheme that uses the conceptlinked list of randomlyembedding the data in theimage and linking themtogether.2. The method proposed in [7]divided the images into equalblock sizes and then useshistogram to embed the data.3. Optimized Bit Plane splicingalgorithm [13] is implementedwhere in the pixels are groupedbased on their intensity andthen the number of bits are torepresent the hidden data arechosen.4. In [16] higher bit planes aregenerated by converting thepixels into different binaryformat using prime numbers asthe weighted function.1. In [17] the authors proposedtwo methods to use the audiosignals to hide the data. In thefirst method, the parity of thesample is checked beforereplacing the LSB of thesample. In the second approachXOR‐ing is carried out.2. In [19] polarity of thereverberations is added to thehigh frequency channels andthese high frequency channelsare used hide the data.1. In [21] the authors haveexploited the redundant fieldslike fragmentation bit and the16‐bit identification field of theIPv4 header to covertly transferthe data over thecommunication network.ACTA TECHNICA CORVINIENSIS – BULLETIN of ENGINEERINGTable Ib: A brief summary of various data hidingtechniques in steganography ‐ Advantage(s)Cover Media Advantage(s)1. StillImage1. The attacker is unable to guessthe next message as the data isnot hidden sequentially. Also,without the password it is notpossible to access the hiddendata.2. Rather than sending a singleimage containing all the hiddendata, blocks of images can besent in out of order to confusethe attacker.3. Since data is hidden in thehistogram it is difficult tolocate the data along with theincrease in capacity to concealdata.4. As the bits are grouped basedon the intensity of the pixels,more number of darkerintensity pixels can be used torepresent the hidden data thanjust the LSB2. AudioSignal3. IPv4Header5. Higher bit planes can now beused to hide the data insteadof just the lower bit planes.1. It is difficult to determine thedata in the audio signalsbecause the data is not hiddendirectly in the sample but theparity is checked beforeinserting the data.2. 1. As the polarity of thereverberations is used to hidethe data in the high frequencysignals, the stego‐audio signalsgenerated are more robust andresistant to errors duringtransmission.1. As the inherent fields of IPv4header are utilized to transferthe data, it is extremelydifficult to detect these covertchannels. Hence, the sensitivedata can be communicatedeasily by using this technique.ISSN: 2067‐3809 [CD‐Rom, online]copyright © UNIVERSITY POLITEHNICA TIMISOARA,FACULTY OF ENGINEERING HUNEDOARA,5, REVOLUTIEI, 331128, HUNEDOARA, ROMANIAhttp://acta.fih.upt.ro2012. Fascicule 3 [July–September] 39
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