Stegonoraphy
- 1. Procedia Computer ScienceProcedia Computer Science 00 (2009) 000–000 www.elsevier.com/locate/procedia ICoCSIM - 2012 Aplication of Steganography Technic For Data Safety Mawaddah Harahapa , Bambang T.J. Hutagalungb , Zilfidarc a,b,c Magister Student of Informatic Departement, University of Sumatera Utara Jl. Universitas No. 24A Medan, 20155,Indonesia Abstract Computer developments and other digital supporting devices have made digital data used more and more. In other hand, the developments have brought about problem deals with copy right and digital material ownership. The hidden message technique (steganography) is a technique that allows the users to hide a message in another message. By the technique, copy right information such as author identity, time and etc can be attached/hidden into some variations of big document like : picture, audio, video text or binary file. This research talks about steganography which denotes a technique that attaches/ hides data while the message that will be attached in used file will be encrypted using algorithm RC4. Key words: hidden message, steganography, RC4 1. Introduction In digital era, communication by computer networks has important role. By electronic communication, someone can make transaction or communication practically. This is an influence of highly significant development of technology of information where the bigger bandwith internet has lower access cost. The consequent is risky of information safety higher. Electronic data information requires significantly different safety device from conventional communication. In traffic information on the internet, conventional authentication system using Identity card, Driving license and etc that focus on signature is invalid. The escort of security officer is not helpful on delivery secure of electronic documents. The simplicity to send messages by electronic media is risky, namely tapping, changing, broken messages so that needs a way to reduce the negative effects of the risk. It will be better if the way can reduce the possible risks. By those reasons, the encoding of the messsages by description and description comes up. *Mawaddah Harahap. Tel.: 061-8221379 ; fax 061-8221379
- 2. Mawaddah Harahap / Procedia Computer Science 00 (2014) 000–000 One of algorithm model used in encoding messages is algorithm Rivest Code 4 (RC4). This model is one of the key of simetric algorithm with stream chipper shape. Algorithm invented on 1987 by Ronal Rivest and it becomes RSA secure symbol (Rivest Shamir Adleman). RC4 uses the key whose length is 1 up to 256 bit and used to initialize table as long as 256 bit. Another method that can be used to encode messages/secret data is steganography, namely hiding data technique on a media. Everyone can show or access the media, however does not realize that the media has been attached a secret message by the sender. Steganography enables the hiding data of any kinds of digital media like document of image, audio, video and text. Theoretically, all files in computer can be used as storage media of message such as, image with JPG, GIF and BMP format, audio with MP3, WAV and also AVI format or another format TXT, HTML, PDF. All files can be hiding place, but it must have redundant bits data that can be modified. After being modified the media file will not much disturb the function and the quality will not be far different. This research focuses on the basic concept to hide electronic data/document especially on image data. The main technique that will be used is steganography using algorithm RC4 to encode messages that will be attached on image file. 2. Objective This research deals with the hidden message concept using stegenography with algorithm RC4. Its aim is to understand the basic characteristics of embedding process and extracting message on steganography and also to build a simple application that can be used to implement hidden message concept. 3. Literary review 3.1. Steganography concept Steganography is a science and an art in hiding communication. Those steganography system hides the content of data in the cover subject that cannot be predicted by common people in order to avoid any prejudices from the people. In the past, people used to have hidden tattoos or ink to convey the content of Steganography. Now, networks technology and computer provide way easy-to-use networks communication for Steganography. Embedding information process in a system of steganography begun by identifying a media cover that possesses excessive bit (can be modified without interfering the integrity of media). The embedding process creates stego medium process by replacing this excessive bit with the data from the hidden messages (figure 1). There are two main processes in digital steganography ; embedding/encoding and extraction messages. The messages can be plain text, chipper text, image or any files, called cover object. Then, the cover object and the attached messages cause stego object. Extraction is a process of outlining hidden messages in the stego media. Stego key can also be used in hidden manner at the time of the next outlining from the message. Simply, steganography is a process of planting embedded message on a cover object, where the result is a stego object. The related parties with steganography are embeddor, extractor and stegoanalyst (Mohanty,1999). Embeddor is a person who performs extraction of stego image by using steganography application. Meanwhile, stegoanalyst is a person who performs stegonalysis. Stegonalysis is a science and an art to detect hidden messages in steganography. 3.2 The differences between Steganography and cryptography Steganography is different from cryptography, the most significant differences are on the output result. In cryptography, the result of data is different from the original form and the data looks like disorganized data so that
- 3. Mawaddah Harahap/ Procedia Computer Science 00 (2014) 000–000 the information is unknown (can be formatted into the original form using description process), while in Steganography has the same form with the original. The same perception is by human sense (especially in visual), however if use computer or other digital devices can be distinguished more clearly between before and after (Suhono, 2000). Figure 2 illustrates the difference between Steganography and cryptography. Fig. 1. (a) steganography; (b) cryptography 3.3 Basic of Embedding There are three different aspects in embedding system of information contradict with one other, namely, capacity, security and robustness. Capacity refers to the amount of information that can be obtained in cover object. Security is prevention to the common people unable to detect hidden information. And robustness is to modify stego subject in order to be able to last against an attack that can disintegrate embedded information. Embedding information is usually related with watermarking and Steganography. The main objective of watermarking system is to get the robustness level to be higher. It is impossible to omit a process of watermarking without lowering the quality of the object data. Steganography, in other hand, to catch up the capacity and security higher, where it is known that the embedded information is easy to know, even small modification to the stego subject can disintegrate it (Provos, 2003). The basic model in embedding is on figure 3(Zolnerr et al., 2004). While figure 4 shows relation between Steganography and watermarking (Suhono et al, 2000). Fig.2. Basic Model of Embedding 3.4 Concept of Dynamic Cell Spreading technique Dynamic Cell Spreading technique is Steganography using protective model against detection developed by Holger Ohmacht with basic concept by embedding file message (all electronic data) into image subject (JPEG). The embedding message is performed by attaching on the lower bit LSB (Least significant Bit) than pixel data that organizes the file using buffering memory as temporary storage media.
- 4. Mawaddah Harahap / Procedia Computer Science 00 (2014) 000–000 In integration process between picture and text, file bitmap 24 bit, so every pixel on the picture consist of three colors, red, green and blue (RGB). Each arrange by numeral 8 byte from 0 up to 225 or using binary format 00000000 up to 11111111. Thus, on each pixel of the bitmap file 24 byte can attach 3 byte data. For instance, the letter A can be attached in 3 pixel, such as original raster data as the following : (00100111 11101001 11001000) (00100111 11001000 11101001) (11001000 00100111 11101001) While representation of binary of letter A is 10000011. By attaching the pixel data above will be produced : (00100111 11101000 11001000) (00100110 11001000 11101000) (11001001 00100111 11101001) It looks there are only four lower bytes changed but it is unseen if we use human senses. At rate, only a half of lower byte data changed, consequently if it is necessary can be used the second lower byte even the third. Integration process of image file using electronic data is almost the same, but it is more complex due to it needs memory as medium to count down the whole sum of byte in the image file or in the electronic data that will be embedded so that will make the embedding process easier. The calculation of arithmetic in doing embedding or extracting uses assembler command due to dealt with bytes in memory. Embedding process in DCS technique has some steps : Make registry address to prepare temporary storage to make calculation process of LSB on picture or data that will be integrated easier. Conversion of JPEG into bitmap (the format of compressed JPEG converted or uncompressed in order to make the calculation and the placement of data easier. Calculating space among the byte on picture to make calculation and attachment of byte data that will be inserted easier. Allocating memory to store byte picture on the process of steganography will be run. Copying bitmap into buffering memory Getting size of input byte file, the same as the process on picture to know the size of the data that will be integrated. Copying buffering memory into bitmap will re-change from memory becomes file picture. Extracting process on DCS technique has some steps : Making registry address to prepare temporary storage to make calculation process of LSB on picture or data that will be extracted easier. Calculating the variables on the sender message namely file picture formatted in bmp. Allocating the size of the memory used. Copying bitmap into buffering memory Extracting size of the file sender into the original size before attaching another file. Calculating variables and re-count after extracting process Extracting file aims at taking data on file picture that have been counted and prepared into previous memory so that the process will run well. 3.5 Algorithm Rivest Code 4 (RC4)
- 5. Mawaddah Harahap/ Procedia Computer Science 00 (2014) 000–000 Rc4 stream chipper denotes one of the type of algorithm that has sBox…….contains per mutation of number 0 up to 255. On algorithm, this encryption will generate pseudorandom byte from the key that will be used in operation Xor against plain text to produce chipper text. To produce default plain text, so its chipper text will get operation Xor against its pseudorandom byte. RC4 uses two kinds of index, I and J in algorithm. Index I is used to ensure that one element changes, while index j will ensure that one element changes random. Briefly, algorithm of stream chipper method divided into two parts, namely : key set up and Rc4 stream cipher generation. On key set up there are three steps; initialization S- Box, saving key in key byte Array, per mutation on S-Box. On the stream generation will produce the value of pseudorandom byte that will get operation Xor to create cipher text or plain text. Algorithm RC4 has two steps, key set up and encryption. Key set up is the first step and the most difficult in algorithm. In key setup N-byte (N is length of key), key of encryption is used to produce variable encryption that use two kinds of array, state and key and the same as-N result of the integration process. 4. Finding And Discussion The finding of this research that uses stegonagraphy application can be seen on table 1 that covers the name of file, type of the format of the picture, the size of the image, attaching status and the size of all successful image. Some of those images showed on fig.3. Table 1. Convers the name of file Filename Format file Size Status Attaching Status Data 1 JPG 19,3 Kb Succesfull 455 Kb Data 2 JPG 16,5 Kb Succesful 675 Kb Data 3 JPG 95,3 Kb No Succesful Data 4 JPG 32,3 Kb Succesful 862 Kb Data 5 JPG 75,5 Kb Succesful 1,05 Mb Data 6 JPG 121 Kb Succesful 901 Kb .JPG 121 Kb .BMP 901 Kb Fig.3. (a) image placeholders; (b) result hidden of message Based on fig.3, at glance looks like there is no difference. This is suitable with the aim of stegonagraphy to attach data on medium storage without having striking spot so that can be concluded that stegonagraphy integration technique DCS and algorithm Rc4 is succeeded.
- 6. Mawaddah Harahap / Procedia Computer Science 00 (2014) 000–000 Embedding process has some forms of method and also implemented program. On the website address www.lecs.com , especially on steganography tool, there are some links to download steganography. The application built using integration between steganography technique and algorithm encryption Rc4. DCS is steganography technique that apply embedding method of data using LSB. The applying of embedding method is performed by preparing a circle of byte, then assigning LSB from the cover based on the value of the second file or data that will be carried. The space between two hidden bytes in sequence becomes the example of this method and will be controlled by a random value, while algorithm Rc4 is used to encrypt messages that will be attached to image, it has purpose that the attached messages are not easy to read. 5. Conclusion By using steganography, so, principly, the problem related with copy right and ownership is solved. This refers to the nature of steganography namely; embedding messages. Thus, steganography is not the only one solution to solve the problem, watermarking and cryptography can also be together solution to overcome copy right and ownership case. DCs technique is embedding process using LSB method. The implementation of the program performed using encoding lower level, assembler. DCS technique has managerial way in allocating memory well in doing embedding process or extracting, so that it does not take much memory. On this steganography program, there is a big changing of the size file, before and after embedding process. In future, needs to do the next research by integrating DCS technique with compressed file of algorithm so that the size of the file of the output process of steganography will be smaller or at least the same as the default and the application of algorithm RC4 method will be attached in file make data more protected. References 1. Henry S, Sayed M, Fitri A (2009), Implementasi Steganografi Dengan Metode Least Significant Bit (LSB). Jurnal Rekayasa Elektrika vol 8, No. 1, 2. Kembanghapsari Rinci, Siti Mariyam. Aplikasi Sistem Pengamanan Data Dengan Metode Enkripsi Menggunakan Algoritma RC4. 3. Rizal, A, Suharto (2011), Implementasi Algoritma Rc4 Untuk Keamanan Login Pada Sistem Pembayaran Uang Sekolah(Studi Kasus : Di Yayasan Yabis Bontang), 142 Dielektrika, ISSN. 2086-9487, Vol2, No.2 4. Mike Y, Miftahul H, Prima K, Implementasi Algoritma Kriptografi RC4 pada Sistem Keaman-an Jaringan Telepon, Proceeding of IES 2008, Surabaya, Januari 2010 5. Maulana, Ahmad M, Data Hiding Steganograph Pada File Image Menggunakan Metode Least Significant Bit, PENS-ITS, Surabaya, 2009 6. Ohmacht, H. (2001). Stegano Project. Diakses pada 23 Februari 2004 dari http://www.holger-ohmacht.de. 7. Popa, R. (1998). An Analysis of Steganographic Techniques. Journal of University Politehnica Timisoara. 8. Provos, N., Honeyman, P. (2003). Hide and Seek: An Introduction to Steganography. IEEE Computer Society. 9. Suhono, Supangkat, H., Juanda, K. (2000). Watermarking Sebagai Teknik Penyembunyian Hak Cipta Pada Data Digital. Jurnal Departemen Teknik Elektro, Institut Teknologi Bandung. 10. Zöllner, J. et al. (2004). Modeling the Security of Steganographic System. Journal of Dresden University of Technology.