Amalgamation of Cyclic Bit Operation in SD-EI Image Encryption Method: An Advanced Version of SD-EI Method: SD-EI Ver-2 Somdip Dey St. Xavier’s College [Autonomous] Kolkata, India E-mail: somdipdey@ieee.org somdipdey@acm.org ABSTRACT In this paper, the author presents an advanced version of image encryption technique, which is itself an upgraded version of SD-EI image encryption method. In this new method, SD-EI Ver-2, there are more bit wise manipulations compared to original SD-EI method. The proposed method consist of three stages: 1) First, a number is generated from the password and each pixel of the image is converted to its equivalent eight binary number, and in that eight bit number, the number of bits, which are equal to the length of the number generated from the password, are rotated and reversed; 2) In second stage, extended hill cipher technique is applied by using involutory matrix, which is generated by same password used in second stage of encryption to make it more secure; 3) In last stage, we perform modified Cyclic Bit manipulation. First, the pixel values are again converted to their 8 bit binary format. Then 8 consecutive pixels are chosen and a 8X8 matrix is formed out of these 8 bit 8 pixels. After that, matrix cyclic operation is performed randomized number of times, which is again dependent on the password provided for encryption. After the generation of new 8 bit value of pixels, they are again converted to their decimal format and the new value is written in place of the old pixel value. SD-EI Ver-2 has been tested on different image files and the results were very satisfactory. KEYWORDS SD-EI, SD-AEI, image encryption, bit reversal, bit manipulation, bit rotation, hill cipher, randomization. 1. INTRODUCTION In modern world, security is a big issue and securing important data is very essential, so that the data can not be intercepted or misused for illegal purposes. For example we can assume the situation where a bank manager is instructing his subordinates to credit an account, but in the mean while a hacker interpret the message and he uses the information to debit the account instead of crediting it. Or we can assume the situation where a military commander is instructing his fellow comrades about an attack and the strategies used for the attack, but while the instructions are sent to the destination, the instructions get intercepted by enemy soldiers and they use the information for a counter-attack. This can be highly fatal and can cause too much destruction. So, different cryptographic methods are used by different organizations and government institutions to protect their data online. But, cryptography hackers are always trying to break the cryptographic methods or retrieve keys by different means. For this reason cryptographers are always trying to invent different new cryptographic method to keep the data safe as far as possible. Cryptography can be basically classified into two types: 1) Symmetric Key Cryptography 2) Public Key Cryptography In Symmetric Key Cryptography [17][20], only one key is used for encryption purpose and the same key is used for decryption purpose as well. Whereas, in Public Key Cryptography [17][19], one key is used for encryption and another publicly generated key is used for the decryption purpose. In symmetric key, it is easier for the whole process because only one key is needed for both encryption and decryption. Although today, public key cryptography such as RSA [15] or Elliptical Curve Cryptography [16] is more popular because of its high security, but still these methods are also susceptible to attack like “brute force key search attack” [17][21]. The proposed method, SD-EI VER-2, is a type of symmetric key cryptographic method, which is itself a combination of four different encryption modules. SD-EI VER-2 method is devised by Somdip Dey [5] [6] [9] [10] [11] [12] [13], and it is itself a successor and upgraded version of SD-EI [5] image encryption technique. The three different encryption modules, which make up SD-EI VER-2 Cryptographic methods, are as follows: 1) Modified Bits Rotation and Reversal Technique for Image Encryption 2) Extended Hill Cipher Technique for Image Encryption 3) Modified Cyclic Bit Manipulation The aforementioned methods will be discussed in the next section, i.e. in The Methods in SD-EI VER-2. All the cryptographic modules, used in SD-EI VER-2 method, use the same password (key) for both encryption and decryption (as in case of symmetric key cryptography). The differences between SD-EI [5] and SD-EI VER-2 methods are that the later one contains one extra encryption module, which is the modified Cyclic Bit manipulation, and the Bits rotation and Reversal Technique is modified to provide better security. www.nitropdf.com 221 International Journal of Cyber-Security and Digital Forensics (IJCSDF) 1(3): 221-225 The Society of Digital Information and Wireless Communications (SDIWC) 2012 (ISSN: 2305-0012)