Fig. 6From: Image encryption using spatial nonlinear opticsRobustness against KPA. a–d The four known plaintext images and e–h the corresponding cyphertext images, i the plaintext image the KPA attempts to reveal, j the retrieved R\(_2\), k the difference between the retrieved R\(_2\) and the original one, and l the result of the KPA. One can clearly seen that the recovered image does not resemble the original plaintext at allBack to article page