DNA Cryptography Based on Symmetric Key Exchange Tausif Anwar #1 , Abhishek Kumar #2 , Sanchita Paul #3 # Dept. of Computer Science & Engg. Birla Institute of Technology, Mesra Ranchi, 835215, India 1 tausifanwar30@gmail.com 2 abhikmr012@gmail.com 3 sanchita07@gmail.com Abstract: - DNA cryptography is a technology of bio science to encrypt large message in compact volume. Now a day, researchers are going to research in the field of secure data transmission. Hiding the encrypted message is important part of Cryptography. Hidden message is in the form of DNA sequence, image, audio and video, which is used to prevent important data from the intruders. In this paper, a new cryptography technique is proposed using Symmetric Key Exchange, one-time pad scheme and DNA hybridization to minimize time complexity.XOR operation with OTP DNA sequence is used as encryption technique based on DNA cryptography. Symmetric Key Exchange is presenting a secure key generation scheme. This method is very efficient in encrypting, hiding, transmitting and preventing powerful attacks. Keywords: -DNA Cryptography, One time pad, DNA technologies, Hiding data. I. INTRODUCTION DNA cryptography is a new field of technology for encrypting any kind of message. Nowadays researchers are focusing on different DNA technologies. There are two ways to realize DNA technology - DNA computing and conventional cryptography. DNA computing uses molecular biology which consists of DNA hybridization, DNA fragmentation and micro biology. According to Adleman, DNA computing is used to solve Hamiltonian path problem [1]. Hamiltonian path problem is finding shortest path to reach from source to destination. He solved seven vertices graph and encoded in molecular structure form, further extend by Lipton to solve NP- complete problem [2]. It has a parallel processing capability with molecular biology and new data structure. DNA cryptography has parallel computing properties to perform the encryption and decryption of the public and private keys. In Public key cryptography same key is used for encrypting and decrypting message and provides security, confidentiality and integrity. A traditional cryptography like DES can be broken by the use of DNA computing [4]. Adleman and Lipton performed DNA polymerase, PCR amplification on DNA strands to encoding of plaintext into binary string [6]. One time pad technique can be used for splitting the DNA sequence and extended in steganogaphy. In modern technology, there is a need of high storage requirement of huge amount of information [7]. DNA cryptography stores huge amount of data in small volume with the combination of only these four letters A, C, G, and T. These bases form the structure of DNA strands by forming hydrogen bonds with each other to keep two strands intact [3]. DNA cryptography based on conventional cryptographic consists of key generation, encryption and decryption process. DNA cryptography achieved the higher level of security while sending data over network. The storage capacity of DNA molecules is (1gm= 10 21 DNA bases) which is equal to (1gm=10 8 tera bytes). This much amount of data is stored, which is efficient for DNA cryptography to reduce space complexity. There are few DNA technologies used in DNA cryptography like polymerase chain reaction (PCR), DNA coding, DNA synthesis. Polymerase chain reaction (PCR) technique is used for encoding a message between two primers. It is difficult to encode a message without knowing the correct primers. Plaintext is encoded in binary code, which is combination of 0 and 1and then it is convert into DNA sequence. DNA coding is based on four nucleotides for encrypting binary to DNA sequence such as adenine ‘A’, cytosine ‘C’, thymine ‘T’ and guanine ‘G’ [9]. Combination of these nucleotides stores information present in all living organisms. The cipher text is completely different from plain text, which is not easily detectable by intruders. James Watson discovered the DNA structure [10]. DNA molecules combined of two single strands which form a double helix structure. There are double hydrogen bond present in between adenine (A) and thymine (T) whereas triple hydrogen bond present in cytosine (C) and guanine (G) [11]. A paired with T and C paired with G to form base pairs to create DNA structure. DNA strands have polarity 5 at the top and 3 at the bottom. A single DNA strands forms a double strands DNA using Hybridization. This paper describes an encryption key exchange method to convert large message into DNA sequence, which reduces time complexity. Tausif Anwar et al. / International Journal of Engineering and Technology (IJET) ISSN : 0975-4024 Vol 7 No 3 Jun-Jul 2015 938