Madhusudan JOSHI^*, Chandra SHAKHER¹, and Kehar SINGH²

The International Centre for Automotive Technology, IMT Manesar, Gurgaon 122050, Haryana, India
¹Instrument Design and Development Centre, Indian Institute of Technology Delhi, New Delhi 110016, India
²Department of Physics, Indian Institute of Technology Delhi, New Delhi 110016, India

(Received January 31, 2009; Accepted May 7, 2009)

A double random phase encoding based digital phase encryption technique for colored images is proposed in the Fourier domain. The RGB input image is brought to HSV color space and then converted into phase, prior to the encryption. In the decryption process the HSV image is and converted back to the RGB format. The random phase codes used during encryption are prepared by stacking three two-dimensional random phase masks. These random phase codes serve as keys for encryption and decryption. The proposed technique carries all the advantages of phase encryption and is supposedly three-dimensional in nature. Robustness of the technique is analyzed against the variations in random phase codes and shuffling of the random phase masks of a given phase code. Performance of the scheme is also verified against occlusion of Fourier plane random phase code as well as the encrypted image. Effects of noise attacks and attacks using partial windows of correct random phase codes have also been checked. Digital simulations are presented to support the idea.

Key words: encryption, decryption, Fourier transform, color, RGB, HSV

^*E-mail address: madhusudanjoshi@gmail.com