CTE: A METHOD TO COMPRESSION - THEN - ENCRYPTION FOR IMAGES

Compression is important because it helps us to reduce the consumption of expensive resources, such as disk space and cost for using bandwidth. Use of the right compression method and encryption technique yield more compact and secure data that are eligible to transfer over public channel. We introduce an optimal approach to compress and then encrypt images. The proposed method is used to increase the compression ratio for images by segmenting an image into non-overlapping segments called edge and non-edge segments and applying different compression depths for these segments. In an edge segment (a region that contains important information) the compression ratio is reduced to prevent loss of information, whereas in a non-edge segment (a smooth region which does not have important information), a high compression ratio is achieved and for encryption a non linear chaotic map is used. The performance of the proposed system is quantified using the peak signal-to-noise ratio to test the compression ratio and also the encrypted image has huge key space which makes harder for hacker to decrypting it using wrong key.