Based on the double random phase encoding,a new method for image encryption using anamorphic fractional Fourier transform(AFrFT) and linear congruence theory is proposed.Random phase masks are generated by using the linear congruential generator(LCG).This encryption algorithm is characterized by that four parameters of the linear function can be keys.The AFrFT has two more fractional orders compared with the conventional FrFT.Since the number of keys increases from 2 to 8 and the proposed algori...