AN APPROACH OF IMAGE ENCRYPTION BASED ON POSITION PERMUTATION AND VALUE TRANSFORMATION Asmita Poojari #1 , Kiran Kumar *2 , Dr. Ganesh Aithal #3 #1 Department of Computer Science and Engineering, NMAMIT Nitte. India #2 Department of Electronics and Communication Engineering, Sahyadri College of Engineering, Mangalore. India #2 Department of Computer Science and EngineeringP.A College of Engineering, Mangalore. India 1 asmipris22@gmail.com 2 kiranvgk@gmail.com 3 ganeshaithal@gmail.com Abstract— With the fast evolution of digital data exchange and increased usage of multimedia images; it is essential to protect the confidential image from unauthorized access. In natural images the values and position of the neighbouring pixels are strongly correlated. The proposed method breaks this correlation of pixel values. This method uses the combination of position permutation and value transformation. Most of the existing encryption algorithm use bitwise operations on the image. The proposed encryption method operates one byte at a time so that other operations such as addition and multiplication can also be applied. In position permutation process of the scheme the image pixels are scrambled using a combination of row shifting and column shifting. Further the resultant image undergoes value transformation process of the scheme wherein each pixel of the original image is substituted using the pseudorandom number sequences generated by Linear Feedback Shift Register (LFSR) using additive, multiplicative and combination method. I. INTRODUCTION With the advent in network technology, information security is an increasingly important issue. Image encryption techniques try to convert an image to another image that is hard to understand; to keep the image confidential between users, in other word, it is essential that nobody could access the content without a key for decryption. Image encryption has a wide range of applications in inter-net communication, multimedia systems, surveillance, medical imaging, telemedicine, and military communication. In order to fulfill such a task, many image encryption methods have been proposed. However, each of them has got their own strengths and weakness in terms of security levels. Cryptography deals with the development of techniques for converting information between intelligible and unintelligible forms. It deals with the content confidentiality and access control. Cryptosystems are divided between those that are symmetric and those that are asymmetric. There is a further division of symmetric cryptosystems into block and stream ciphers. Block ciphers operate with a fixed transformation on large blocks of plaintext data; Stream ciphers operate with a time varying transformation on individual plain-text digits. Stream ciphers are fast and simple compared to block ciphers. The main challenge in Stream Cipher Cryptography is the generation of a long unpredictable key sequence from seed key [1]. The image encryption algorithms can be classified into three major groups: i. Position permutation based algorithm ii. Value transformation based algorithm iii. Visual transformation based algorithm. II. PROPOSED SYSTEM The proposed encryption algorithm makes use of two types of classification techniques i.e. position permutation and value transformation. The main idea behind the proposed method to encrypt digital images is trying to create an easiest and high secure encryption and decryption method that creates good confusion i.e. making the relationship between the plaintext and the cipher text as complex and involved as possible and good diffusion i.e. the redundancy in the statistics of the plaintext is "dissipated" in the statistics of the cipher text in the encrypted image. Also algorithm operates on one byte rather than one bit and hence addition and multiplication operations are applied on the image pixels. The proposed technique involves three phases of encryption process. The first phase is the random number generation phase wherein pseudorandom numbers are generated which are used as keys in the encryption process. The next phase is the position permutation phase where the image pixels are scrambled. The last phase is the value transformation phase where each pixel of the original image is substituted using the pseudorandom number sequences generated by Linear Feedback Shift Register (LFSR) using additive, multiplicative and combination operations. All the three methods of operation are compared and experimental results shows which works the best among the three. The proposed architecture is shown in figure 1. Phase 1: Pseudorandom number generation