Study on the influence of key errors on the deciphered image in the double random phase encryption system by applying affine cryptography

In this paper, an explanation of the double random phase encryption technique using affine cryptography is proposed. The principle of this technique to decipher an optical image may be regarded as an optical realization of the affine cryptography. During the deciphering process of double random phase encryption based on the 4-f optical system, if there are errors in the random phase, which plays as a decryption key, these errors will be added to the encrypted image in the form of noise. The signal-to-noise ratio of the decrypted image has been analysed under the situation that the errors had occurred, both in the position of lateral direction and the value of the pixel function from the random phase mask. Furthermore, the fault tolerance of orientation in the decipher system has been discussed when only a part of the random phase mask is used.