The double random phase encoding technique is examined to determine how, for both amplitude encoding (AE) and phase encoding (PE), the two decryption keys (the image and Fourier planes) affect the output gray scale image when they are in error. The decrypted images in the figure result from increasing amounts of random distribution of incorrect pixel values, which can represent an attacker having a partial key, in the Fourier plane, with (a) AE (note the Gaussian type noise), or (b) PE, or (c) partial image-plane key for PE (note the "salt and pepper" type noise). In (d) both keys are simultaneously in error for PE. For details, see the paper by Monaghan et al., pp. pp. 3808-3816.