In this paper, a new image block cipher encryption strategy for gray scale images using a different set of secret key and sizes is proposed. Initially, the swapping and dispersion is done without keys and in second stage the image is mixed with the chirikov map involving first secret key. 'N' rounds are taken to complete this process. The blended image is divided into blocks of block size 8X8. These blocks are also swapped to achieve good confusion. For making the encryption scheme more sturdy in each block the transmutation of pixels is done with the modified logistic map having three more secret keys.