Importance to security in every application on internet is a clear motivation to contribute in the field of Information Security. Security is one of the most challenging aspects in the internet and network applications. When it is desired to transmit redundant data over an insecure and bandwidth-constrained channel, it is customary to first compress the data and then encrypt it. In this paper, reverse the order of these steps, i. e. , first encrypting and then compressing, without compromising either the compression efficiency or the information-theoretic security. Here, all through the use of coding with side information principles, this reversal of order is indeed possible without loss of either optimal coding efficiency or perfect secrecy. In addition to proving the theoretical feasibility of this reversal of operations, a system which implements compression of encrypted data is described. The image encryption technology based on chaos theory is used which have been developed to overcome the disadvantages present in traditional encryption techniques. In this paper a chaotic based encryption technique followed by compression by SPIHT algorithm and their results are compared.

1. Sanjeev Ghosh, Sangeeta Mishra, Payel Saha. Chaos Based Encryption Technique for Digital Images. 2010 International conference ICWET.
2. Marc Van Droogen broeck and Raphael Benedett, Techniques for a selective encryption of uncompressed and compressed images. Proceedings of ACIVS 2002 (Advanced Concepts for Intelligent Vision Systems), Ghent, Belgium, September 9-11, 2002
3. Zhang Dinghies, GU Qiujie, Pan Yonghua and Zhang Xinghua. 2008. Discrete Chaotic Encryption and Decryption of Digital Images. 2008 International Conference on Computer Science and Software Engineering.
4. Huang-Pei Xiao and Guo-Ji Zhang. 2006. An Image Encryption Scheme Based on Chaotic Systems. Proceedings of the Fifth International Conference on Machine Learning and Cybernetics, Dalian, 13-16 August 2006. [5 Jiri Fridrich. 1997. Image Encryption Based on Chaotic Maps. Proceedings of IEEE Conference on Systems, Man and Cybemetics. 1105-1110, 1997.
5. S Wang Ying, Zheng, DeLing Ju Lei, et al. 2004. The Spatial-Domain Encryption of Digital Images Based on High-Dimension Chaotic System. Proceeding of 2004 IEEE Conference on Cybernetics and Intelligent Systems, Singapore, pp. 1172-1176, December. 2004.
6. Huang Xiaosheng, Gu Jingwen. Image Encryption Algorithm Based on Compound Chaotic Sequence and Wavelet Transform [J]. 2007. Computer Engineering, 200733(14): 128-129,135.
7. Sobhy, M. I. and Shehata, A. R. Methods of Attacking Chaotic Encryption and Countermeasures. 2001. IEEE Proceedings of ICASSP 2001, Vol 2, pp. 1001-1004 May. 2001.
8. D. Slepian and J. K. Wolf, "Noiseless coding of correlated information sources," IEEE Trans. Inform. Theory, vol. IT-19, pp. 471–480, July 1973.
9. Mark Johnson, Student Member, IEEE, Prakash Ishwar, Vinod Prabhakaran, Student Member, IEEEOn Compressing Encrypted DataIEEE TRANSACTIONS ON SIGNAL PROCESSING, VOL. 52, NO. 10, OCTOBER 2004

Image Encryption Chaos Theory Spiht Algorithm Image Decryption