5. Conclusion:
A new secure efficient bi-step quantum images cryptography algorithm is proposed. Here, four different coding algorithms are introduced. In this scheme, for the aim of completing the coding task, a randomized binary image key is generated during the procedure.
In the coding process, based on both the pair of original images pixels and their corresponding quantum bits of the generated randomized key, the coding algorithm is selected. In each coding step, the key image not only is used to select the applying coding algorithm for each pixel, but also some qubits of the key is used directly to change the grayscale value of the pixel. This means that if one doesn’t have the randomized key images, it is impossible for him to decode the original image correctly.
From the experimental results, it can be seen that the proposed algorithm codes different kinds of images very well and the final coded images were completely meaningless. In each case, the histogram diagram of the final coded image is so much flatter than the histogram diagrams of the original and once coded images. Also, in each case, the calculated entropy of the twice coded image is higher than the calculated entropy of original and once coded images, which confirms that the proposed coding process imposed a considerable uncertainty to the original image.
