Compression and Encryption Algorithms for Image Satellite Communication

Satellite communication systems are now designed according to an outdated Shannon information theory where all data is transmitted in meaningless bit streams. The advantages for satellite communication may include: high image compression and unbreakable encryption. So, this paper combines the compression and encryption techniques into two phases, encoding and decoding phase. The fractal compression technique is selected to compress the aerial images due its high compression capability and the Enhanced Hill Multimedia Cryptosystem (EHMC) is used for encryption to perform the goal. The fractal image compression of the input aerial image is the first stage in the encoding phase. The fractal compression technique divides the original image into two different block sizes called range and domain blocks. The best match between the range and domain blocks is known as the transformation mapping. All the transformation mappings are recorded as the output compressed file of the input aerial image. The encryption which was done by the EHMC is the second encoding stage The EHMC belongs to the private-key techniques and works with linear transformation theory is applied on the output-compressed file. At the decoding phase, the secured compressed image is decrypted by the EHMC. Finally, the original image is reconstructed from the highly secured compressed file using the fractal decompression process. The objective of the paper is to provide an approach in the area of robust encrypted compression techniques, which achieve the privacy and confidentiality of aerial and remote sensing images transmitted over an insecure channel from unauthorized access.