Int. J. Tech. 2011; Vol. 1: Issue 1, Pg 12-14
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2231-3907 (Print)
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2231-3915 (Online)
RESEARCH ARTICLE
Experimental Investigation of Image Encryption Technique Using Public Key Rajneesh Kumar and Umesh Chandra Jaiswal M.M.M Engineering College Gorakhpur, India *Corresponding Author E-mail:
[email protected]
ABSTRACT:
The presence of computer networks has prompted new problems with security and privacy. Having a secure and reliable means for communicating with images and video is becoming a necessity and its related issues must be carefully considered[1]. Hence, network security and data encryption have become important. The images can be considered nowadays, one of the most usable forms of information. Image and video encryption have applications in various fields including Internet communication, multimedia systems, medical imaging, telemedicine and military communication. So image encryption plays a very crucial role in network security. Image encryption is classified in two categories Private key cryptography and Public key cryptography. This paper focus image encryption using public key of 128* 128 block[10]. In the case of public key image encryption sender and receiver use different key for encrypting and decrypting.
KEYWORDS: Image, Encryption, Decryption, Public key, private key. INTRODUCTION:
We are living in the information age; we need to keep information about every aspect for our lives. In other words, information is an asset that has a value like any other asset. As an asset, information needs to be secured from attacks[4]. During the last two decades, computer networks created a revolution in the use of information. Authorized people can send and receive information from a distance using computer networks[5]. To be secured, information needs to be hidden from unauthorized access (confidentiality), protected from unauthorized change (integrity), and available to an authorized entity, when it is needed (availability). Although the three previously mentioned requirements have not changed, they now have some new dimensions[10]. Not only should information be confidential, when it is stored in a computer; there should also be away to maintain its confidentiality, when it is transmitted from one computer to another [16]. Information transmitted over computer networks nowadays is not only text, but also audio, image, and other multimedia types[12]. The field of multimedia security has matured in the last decade to provide a class of tool-sets and design insights for the protection and enhancement of digital media under a number of diverse attack scenarios.
Research in multimedia security was first motivated, in part, by the increasing use of digital means to communicate, store and represent entertainment information such as music and video. The digital form allowed the perfect duplication of information and almost seamless manipulation and tampering of the data[10]. This created new types of security attacks not (as seriously) addressed in the past by the entertainment industry. The paradigm shift from analog to digital multimedia for entertainment has had an enormous impact for artists, publishers, copyright holders and consumers alike providing flexible and more accessible business models [17]. In such a setting, one natural question that arises is the security and confidentiality of a digital packet of multimedia information[12]. Pubic Key Encryption:
Received on 11.03.2011 Accepted on 22.03.2011 © EnggResearch.net All Right Reserved Int. J. Tech. 1(1): Jan.-June. 2011; Page 12-14
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Proposed Approach: A: Encryption: • Dividing original image into distinct P × P blocks and transforming them into DCT domain, the corresponding DCT coefficients are named as XM×N. XM×N = DCT (I, [P P]) ... (1) • Encrypting the frontal K×K coefficients of every P×P block, respectively. Let X1 denotes the matrix composed by the frontal K ×K coefficients of certain P ×P block X0, the corresponding encryption formula by using the private key AU can be described as X2 = AUX1 ... (2) • Replacing the frontal P × K coefficients of X0 with X2 R P×K. If K is close to P, according to the characteristic of DCT coefficients, the rest (P -K) × (P - K) coefficients are all close to 0. So we can directly replace them and the decrypted image is almost not influenced. X0 (i, j) = X2 {1= i = P, 1 = j= K} ... (3) • Making the inverse DCT transformation and uniting all P ×P blocks, the final result is defined as X2 M×N = IDCT (XM×N) ... (4) • Keeping all the transformed coefficients between 0 and 1[5]. % Get the minimum of X2 M×N named as Min i.e Min = max((-1) x X2 M×N % Ensure all the coefficient of X2 M×N more than 0 i.e X2 M×N = X2 M×N +Min % Get the maximum of updated X2 M×N named as Max i.e Max =max(X2 M×N) % Ensure all the coefficient of X2 M×N less than1 i.e X2 M×N = X2 M×N / Max ... (5) • Saving the encrypted image as jpg file.
Because the column vector of U is a set of orthonormal bases, it is easily proved: UtU = E. So, we can draw the conclusion: • D 2 = X0 ... (9) • Replacing the frontal P × K coefficients of D0 with D2 and 0.
… (10) • Making the inverse DCT transformation and uniting all P ×P blocks, the final result is defined as X5M×N. X5M×N = I DCT (X4M×N) ... (11) • Saving the decrypted image as jpg file. Experimental Result:
Fig 1: Proposed System
B: Decryption: The decryption operation is a usual correlation process with five elements: (1) block length P (2) encryption matrix dimension K (3) public key A-tU (4) the coefficient minimum Min (5) the coefficient maximum Max. Suppose X3M×N denotes the encrypted image, the details of decryption are following [6]: • Recovering all coefficients of X3 M×N Fig 2: Menu for Image Encryption • X3 M×N = X3 M×N × Max -Min ... (6) • Applying DCT transformation to each distinct P × P block of X3 M×N X4 M×N = DCT (X3 M×N, [P P]) ... (7) • Decrypting the frontal P ×K coefficients of every P × P block, respectively. Let D1 denotes the matrix composed by P ×K coefficients of certain P×P block D0, the corresponding decryption data D2 2 RK×K by using the public key A-t U can be given as following: • D 2 = (A-t U) t D1 • D 2 = (Ut A-1 ) (AU) X0 ...(8 • D 2 = (Ut U) X0 Fig 3: Input Image
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CONCLUSION:
Fig 4: Encrypted Image
In this paper, we presented a new public-key encryption scheme based on non-expansion visual cryptography a[13]. Our scheme allows one party to send a secret image to another party over the open network, even if many eavesdroppers listen. Therefore, our scheme can be useful in many applications. Our scheme gives reliable security [11]. We presented a new image encryption/decryption scheme based on matrix transformation in this paper[9]. The salient features of the proposed asymmetric image encryption scheme can be summarized as: (a) Lossless encryption of image. (b) Less computational complexity. (c) Convenient realization.(d) Choosing a suitable size of matrix according to the size of image.(e) Encryption/decryption scheme uses integer arithmetic and logic operations. It requires minimized computational resources[7].
REFERENCES: 1. 2. 3. 4. Fig 5: Save Encrypted Image
5.
6. 7. 8. 9. 10. 11. Fig 6 : Decrypted Image
12.
13. 14. 15. 16.
Fig 7: Save Decrypted Image
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