IMAGE ENCRYPTION USING DNA AND BLOCK BASED CIPHER

Abstract

ABSTRACT The blowfish algorithm is a block based encryption symmetric key encryption algorithm and has many advantage in symmetric data encryption. But when we encrypt an image which has large block of single colour than after encryption it convert this block to same but different colour so it may be easily to understand that this large block has single colour so any has crack the image. So we add DNA cryptography to improve the encryption algorithm. DNA cryptography encrypt data at bit level. In this thesis logistic map is used to generate the DNA sequence. To improve the randomness in generating the DNA sequence, we generate the initial value of logistic map using blowfish key, so every time DNA sequence is different on different blowfish key. Initial value of logistic map is calculated using hash function. In the first stage of this approach the image will be converted into DNA sequence and another DNA sequence will be generated using logistic map then DNA addition operation is performed. After anti clockwise rotation is performed on output then output is feed to blowfish algorithm. The output is measured for the security level based on correlation, histogram and entropy. The experiment results have shown that the combination technique resulted in a higher entropy value and lower correlation and more uniform histogram.