DNA computing is new wave of advancement in the field of cryptography. DNA is an ultra compact information storage medium with high security and theoretically unbreakable algorithm. We present a new technique for securing the image using DNA computing. In practical steganography images can be broken with some assumption on the information theoretic entropy of the plaintext. We discuss a modified DNA sequencing algorithm for encoding image which appear to be more secure. The image is converted to DNA code and divide into fragments. The fragments are sorted and cloned as a bacterial library which acts as cipher. The clones are extracted from the DNA mixture and decrypted using the DNA sequencing technique, Greedy Shortest Common Substring algorithm(GSCS). This algorithm takes the advantage of decreasing the time complexity and increasing the rate of accuracy in the field of image cryptography.