International Journal of Scientific & Engineering Research, Volume 4, Issue 7, July-2013 150 ISSN 2229-5518 IJSER © 2013 http://www.ijser.org IMAGE ENCRYPTION AND DECRYPTION USING BLOWFISH ALGORITHM IN MATLAB Pia Singh Prof. Karamjeet Singh Abstract: With the progress in data exchange by electronic system, the need of information security has become a necessity. Due to growth of multimedia application, security becomes an important issue of communication and storage of images. This paper is about encryption and decryption of images using a secret-key block cipher called 64-bits Blowfish designed to increase security and to improve performance. This algorithm will be used as a variable key size up to 448 bits. It employs Feistel network which iterates simple function 16 times. The blowfish algorithm is safe against unauthorized attack and runs faster than the popular existing algorithms. The proposed algorithm is designed and realized using MATLAB. KEYWORDS: Cryptography, Image encryption, Decryption, Blowfish, Block Cipher. I. INTRODUCTION Because of the increasing demand for information security, image encryption decryption has become an important research area and it has broad application prospects. The field of encryption is becoming very important in the present era. Image security is of utmost concern as web attacks have become more and more serious. Image encryption decryption has applications in internet communication, multimedia systems, medical imaging, telemedicine, military communication, etc. Many image content encryption algorithms have been proposed. To make the data secure from various attacks and for the integrity of data we must encrypt the data before it is transmitted or stored. Government, military, financial institution, hospitals and private business deals with confidential images about their patient (in Hospitals), geographical areas (in research ), enemy positions (in defense), product, financial status. Most of this information is now collected and stored on electronic computers and transmitted across network to other computer. If these confidential images about enemy positions, patient and geographical areas fall into the wrong hands, than such a breach of security could lead to declination of war, wrong treatment etc. Protecting confidential images is an ethical and legal requirement. Fig: Encryption/Decryption Process. So in this paper we are implementing blowfish algorithm which is strongest and fastest in data processing/storing compare to other algorithms. Blowfish algorithm is highly secured because it has longer key length (more no of key size). The philosophy of proposal algorithm is to use the full menu of “Strong operations” supported in modern computers to achieve better security properties and provide high speed. The main aim behind the design of this proposal is to get the best security/performance tradeoff over existing Web Images. II. BACKGROUND Image encryption schemes have been increasingly studied to meet the demand for real-time secure image transmission over the Internet and through wireless networks. Encryption is the process of transforming the information for its security. With the huge growth of computer networks and the latest advances in digital technologies, a huge amount of digital data is being exchanged over various types of networks. It is often true that a large part of this information is either confidential or private. The security of images has become more and more important due to the rapid evolution of the internet in the world today. The security of images has attracted more attention recently, and many different image encryption methods have been proposed to enhance the security of these images. Image encryption techniques try to convert an image to another one that is hard to understand. On the other hand, image decryption retrieves the original image from the encrypted one. There are various image encryption systems to encrypt and decrypt data, and there IJSER