In recent years, various DNA based cryptographic algorithms have been suggested to develop secure image encryption techniques but still many of them have low computing security as they have low avalanche effect which is the required property of a good cryptographic algorithm. In this regard, this book proposes a new method of image encryption based on DNA computation technology. The original image is encrypted using DNA addition and DNA complementary rule. First, a secret key is generated using a DNA sequence and modular arithmetic operations. Then each pixel value of the image undergoes the encryption process using the key and DNA computation methods. The validity of the algorithm is proven through simulation and the theoretical analysis on the parameters such as sensitivity to plaintext, key sensitivity, histogram analysis, correlation analysis including bio-security and math security. Further, the algorithm has a huge key space generated using key expansion algorithm while keeping the original key sequence small. It is shown that the algorithm has achieved the satisfactory computing-security level in the encryption security estimating system.