Journal of Global Research in Computer Sciences
MenuISSN: 2229-371X
ISSN: 2229-371X
Ramveer Singh1 ,Awakash Mishra2, Sanjive Tyagi 3and Deo Brat Ojha4
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In our day to day life, requires more secure transmission whereas the transmission channel is too noisy. Transmission image in various field i.e. medical field (Telemedicine) with complete efficiency for saving human life, secrecy of communication between secret agents and their relative government, to maintain the confidentiality in military operations, etc. In our approach, we introduced a new scheme to transmit an image over noisy transmission channel. Our approach is suitable combination of cryptography and compression with removal of transmission error. Cryptography provides secure transmission, Compression increases the capacity of transmission channel and Fuzzy is used for error which gets during transmission of image.
Keywords |
| Image, Compression, Encryption, Decryption, Secure Communication, Error Detection & Correction. |
INTRODUCTION |
| The amount of image has increased rapidly on the Internet. Image Two different approach of technologies have been developed for this purpose. The first approach is based on content protection through encryption [1], [2]. Cryptography is a branch of applied mathematics that aims to add security in the ciphers of any kind of messages. Cryptography algorithms use encryption keys, which are the elements that turn a general encryption algorithm into a specific method of encryption. The data integrity aims to verify the validity of data contained in a given document. [3]. |
| In addition, to avoid sending files of the enormous size, a compression scheme can be employed what is known as lossless compression on secrete message to increase the amount of hiding secrete data, a scheme that allows the software to exactly reconstruct the original message [4]. The transmission of numerical images often needs an important number of bits. This number is again more consequent when it concerns medical images. If we want to transmit these images by network, reducing the image size is important. The goal of the compression is to decrease this initial weight. This reduction strongly depends of the used compression method, as well as of the intrinsic nature of the image. Therefore the problem is the following: 1. To compress without lossy, but with low factor compression. If you want to transmit only one image, it is satisfactory. But in the medical area these are often sequences that the doctor waits to emit a diagnostic. |
| 2. To compress with losses with the risk to lose information. The question that puts then is what the relevant information is to preserve and those that can be neglected without altering the quality of the diagnosis or the analysis. The human visual system is one of the means of appreciation, although subjective and being able to vary from an individual to another. However, this system is still important to judge the possible causes of degradation and the quality of the compression [5]. In this scheme, we introduce effective approach to transmit an secure and compressed image over noisy transmission channel. |
PRELIMINERIES |
| Enhanced Data Encryption Standard (EHDES) |
| Enhanced Data Encryption Standard (EHDES) [6] , [7], uses the block of data and a symmetric key. As traditional Data Encryption Standard (DES), it also breaks data string into 64-Bit blocks and follows three phases: 1. Key Generation. 2. Encryption on Input Data. 3. Decryption on Input Cipher. |
| Key Generation |
| In this phase of EHDES moderate the initial 56 Bit key using Random Number Generator (RNG) for every block of message (M1, M2, M3 ...Mn). The new generated 56 Bit keys (Knew1, Knew2, Knew3................ Knew n. For every Mi EHDES generate Knew i, applying F on generated random number (NRNG) and the initial key K. |
| Encryption on Input Data |
| Message breaks in 64 Bit n blocks of plain text. |
| M = {M1, M2, M3... Mn} |
| Now, we encrypt our message {M1, M2, M3,...................., Mn} blocks by each new generated key Knew1, Knew2, Knew3................ Knew n and generated |
| C={C1, C2, C3,................ Cn}. |
| Decryption on Input Cipher |
| Decryption is the reverse process of encryption and also used the same key which is used in encryption. |
| The SEQUITUR Algorithm [8] |
| The SEQUITUR algorithm represents a finite sequence _ as a context free grammar whose language is the singleton set {s}. It reads symbols one-by-one from the input sequence and restructures the rules of the grammar to maintain the following invariants: |
| • no pair of adjacent symbols appear more than once in the grammar, and • every rule (except the rule defining the start symbol) is used more than once. |
| To intuitively understand the algorithm, we briefly describe how it works on a sequence 123123. As usual, we use capital letters to denote non-terminal symbols. After reading the first four symbols of the sequence 123123, the grammar consists of the single production rule S 1, 2, 3, 1 where S is the start symbol. On reading the fifth symbol, it becomes S 1, 2, 3, 1, 2 Since the adjacent symbols 1, 2 appear twice in this rule (violating the first invariant), SEQUITUR introduces a non-terminal A to get |
| S A, 3,A A 1, 2 Note that here the rule defining non-terminal A is used twice. Finally, on reading the last symbol of the sequence 123123 the above grammar becomes S A, 3, A, 3 A 1, 2 This grammar needs to be restructured since the symbols A, 3 appear twice. SEQUITUR introduces another non-terminal to solve the problem. We get the rules S B,B B A 3 A 1 2 However, now the rule defining non-terminal A is used only once. So, this rule is eliminated to produce the final result. S B, B B 1, 2, 3 Note that the above grammar accepts only the sequence 123123. |
| Block Error Rate |
| The application's block error rate can be computed from the bit error rate using the following equation |
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| N is the number of bits in a block, E is the number of errors in a block and p is the probability of a bit error (bit error rate) |
| This equation basically states that the block error rate is dependent on three factors: |
| The number of statistical combinations of failing bit patterns (E combinations of N), |
| The probability of E errors occurring (p raised to the E power), and |
| The probability of N-E correct data bits ((1-p) raised to the N-E power). |
| Error Correction Code |
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OUR SCHEME |
| A complete transmission process includes the following steps: |
| Step 1: Generating n*n blocks: |
| In RGB space the image is split up into red, blue and green images. The image is then divided into blocks of pixels and accordingly the image of pixels will contain blocks. Where, . |
| Step 2: DCT: All values are level shifted by subtracting 128 from each value. The Forward Discrete Cosine Transform of the block is then computed. The mathematical formula for calculating the DCT is: |
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| Step 3: Quantization: Quantization is the step where the most of the compression takes place. DCT really does not compress the image, as it is almost lossless. Quantization makes use of the fact that, the high frequency components are less important than the low frequency components. The Quantization output is |
 |
| The matrix could be anything, but the JPEG committee suggests some matrices which work well with image compression. |
| Step 4: Compression using SEQUITUR: After quantization, the scheme uses a filter to pass only the string of non-zero coefficients. By the end of this process we will have a list of non-zero tokens for each block preceded by their count. DCT based image compression using blocks of size 8x8 is considered. After this, the quantization of DCT coefficients of image blocks is carried out. The SEQUITER compression is then applied to the quantized DCT coefficients. The compression achieved in this approach is evaluated based on the overall compression ratio (CR) which is defined as: |
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| Step 5: Encryption using EHDES: In encryption phase, EHDES take output of compression phase as a message block WX and a new generated key YXZ[X implement encryption process as per traditional DES. In this process, New key is also make 16 different key for every round of EHDES using shifting property as per traditional DES. For every block of message M, new key YXZ[X makes a new key block for every round of DES to implement in the encryption process. Decryption Process is the inverse step of encryption process. In decryption, we also use the same key which is used in encryption. |
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SECURITY ANALYSIS |
| We verified that the compression ratio of Sequitur outperforms Gzip as well as Compress. On the other hand, however, the compression and decompression are very slow compared to Gzip and Compress, because Sequitur utilizes the arithmetic coding that is time consuming, and the program might not be fully optimized. From our view point of compressed pattern matching, compression time is not a serious matter, while the decompression time is critical. In the original program of Sequitur, decompression routine borrows the same data structures, such as doubly linked list, that are unnecessary for decompression only. Thus we simply rewrote the decompression routine using a standard array. Cryptographic scheme strength is often described by the bit length of encryption key. The more bits in the key, the harder it is to decrypt data simply by all possible key. DES uses 56 bit, Cracking 56- bit algorithm with a single key search might take around a week on a very powerful computer. |
| Now, |
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CONCLUSION |
| Our scheme provides the complete security and compressed form of image, which provide the maximum efficiency to transmission channel. If some error is produced by channel, the fuzzy error correction code remove the error and provide to user more perfect image. |
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References |
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