Comments on "A Novel Compression and Encryption Scheme Using Variable Model Arithmetic Coding and Coupled Chaotic System"

Jiantao Zhou, Oscar C. Au

Abstract: para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> Recently, Bose and Pathak proposed a joint compression-encryption scheme by incorporating an adaptive arithmetic coder with a coupled chaotic system <citerefgrp> <citeref refid="ref1"/></citerefgrp>. In this comment, we first show that the scheme proposed by Bose and Pathak <citerefgrp><citeref refid="ref1"/> </citerefgrp> is not decodable. It is due to the fact that the current symbol to be encoded is swapped with a randomly selected symbol in the model prior to encoding it, making it impossible for the decoder to mirror the encoder's operations. We then suggest a natural solution to solve the undecodability problem by using the last encoded symbol to swap. Unfortunately, it can be shown that this modified scheme is vulnerable against a chosen-plaintext attack. </para>