Research On Joint Compression And Encryption Algorithms And Their Implementation

Since the first masterpiece from Shannon was published,information theory has aroused great attentions and made a tremendous impact on many other research fields,such as computer science,cryptography,and communication,etc.Of the numerous research directions in information theory,source coding has been an indispensable part of communication system,especially after the emerging of arithmetic coding and Lempel-Ziv coding.Despite of the highly efficient compression algorithms,their insecurity has been revealed since the end of 20th century.In order to remedy this shortcoming,a simple solution is to make the compression algorithms followed by a secure encryption standard,such as AES and triple DES.Nevertheless,since both stages are time-consuming,this approach,without doubt,dramatically increases the use of computational resources.Recently,a new approach named joint compression and encryption has been proposed.Due to the fact that this method is capable of combining compression and encryption,it can be considered as a perfect solution to the aforementioned problem.There are,to date,mainly two different kinds of simultaneous compression and encryption schemes.These two approaches can be achieved by either adding cryptography concept in compression schemes or embedding compression mechanism into encryption algorithms.Many works based on arithmetic coding utilize the first approach to realize joint compression and encryption these years but most of these schemes are shown insecure and inefficient.For the second approach,albeit its insecurity has not been found yet,its compression ratio is unsatisfactory,even worse than Huffman coding.The focus of this thesis is on designing more secure and efficient algorithms so as to overcome the drawbacks of present algorithms based on arithmetic coding.For the first approach,the compression efficiency of present algorithms is first analyzed,and then,a more generalized definition of arithmetic coding is presented.It is shown that the present joint compression and encryption schemes for arithmetic coding are all the special cases of the proposed scheme.Meanwhile,a universal method for developing new joint compression and encryption schemes is introduced.With regard to the second approach,a more advanced version is presented.By contrast,the compression efficiency and running time of the proposed scheme and the old versions are shown.Experimental results and some analysis verify the security and high efficiency of the proposed scheme.