International Journal of Computer Science Trends and Technology (IJCST) – Volume 4 Issue 1, Jan - Feb 2016 ISSN: 2347-8578 www.ijcstjournal.org Page 23 Symmetric Encryption Scheme Using Logistic Map K.Saranya [1] , AG.Shanmathi [2] , N.Suchitra [3] , Dr.S.Ramakrishnan M.E. Ph.D [4] UG Students [1], [2], [3] , Professor and Head [4] Department of Information Technology Dr. Mahalingam College of Engineering and Technology Coimbatore – 642003 Tamil Nadu - India ABSTRACT With modern technological advancements, multimedia messages overpower the usage of text messages. These messages are usually exchanged using the internet. Security threats are drastically increasing over the internet. In such a scenario, the need for security enhancements during the multimedia exchange becomes unavoidable. Security measures can be taken by collaborating cryptographic techniques with image processing. Grey scale images are dealt here. The original image is first permuted using logistic map. The same is done on a cover image. The permuted pixel values of the original cover image are then substituted with the summation of corresponding pixel values of the resultant permutation pixel values of the original and the cover image. Thus it is difficult for the attackers to decrypt the original image because the attackers have no knowledge about the cover image. The attacker should also know the exact parameters used for the logistic maps to get the original image, which is very difficult to guess. In this proposed approach, grey scale image encryption using logistic maps is immune to attacks. Various result analysis techniques like histogram analysis, entropy analysis, Number of Changing Pixel Rate analysis and correlation coefficient analysis has been proposed to analyse the result. Thus this approach is used for secure transmission of grey scale images in an open network. Keywords:- Permutation, Substitution, Chaotic Map, Logistic Map, Number of Changing Pixel Rate, Correlation. I. INTRODUCTION Cryptography: Cryptography is the art and science of keeping messages secure. This relates to various types of aspects in information security such as data confidentiality, data integrity, authentication and non-repudiation. A cryptographic algorithm, or cipher, is the mathematical function used for encryption/decryption which involves converting the original images into another form, for the purpose of security. Encryption and Decryption: Based on cryptographic principles, Encryption is the process of translating original data (plaintext) into a random, meaningless data (cipher text). Decryption is the process of converting cipher text back to plaintext. This is usually done with the help of a special knowledge called key.Image Encryption is a notable domain where numerous research activities are carried out these days. Encryption involves converting data or information from its original form to an unpredictable hidden form making it tedious for retrieval. Protecting the image data from Unauthorized access is important. Encryption is employed to increase the image security. Fig.1.Structure of Image Encryption Permutation and Substitution: Permutation technique is the one in which the plaintext remains the same, but the shuffling occurs in the order of the characters. It refers to the act of reordering the smallest data unit according to some algorithm. To be effective, any no uniformity of plaintext data units has to be redistributed across the cipher text, making that no uniformity much harder to detect. Substitution technique is one in which each character in the plaintext gets substituted for some other character in the cipher text. The receiver inverts the substitution on the cipher RESEARCH ARTICLE OPEN ACCESS