ABSTRACT :
This paper presents a new method, of recompressing a JPEG
crypto-compressed image. In this project, we propose a cryptocompression
method which allows recompression without any information
about the encryption key. The recompression can be executed
on the JPEG bitstream directly by removing the last bit of
the code representation of a non null DCT coefficient and adapting
its Huffman code part. To be able to apply this approach,
the quantization table is slightly modified to make up the modifications.
This method is efficient to recompress a JPEG cryptocompressed
image in terms of ratio compression. Moreover, since
the encryption is fully reversible, the decryption of the recompressed
image produces an image that has a similar visual quality
compared to the original compressed image.