Abstract: The security of image has become an important topic in the process of storage of an image and transmission of image over an unsecured channel such as internet. This paper proposes a new approach for colour image encryption and decryption using involuntary matrix associated with Arnold transformation. In this paper computer simulation with standard examples and the experimental results are given to support the robustness of the scheme. Sensitivity analysis and a comparison between earlier proposed techniques with our proposed approach is also given in this paper.

Keywords: Colour image encryption, Colour image decryption, involutory matrix, Arnold transforms, cryptosystem.