Cryptanalysis and improvement of an image encryption algorithm based on chaotic and Latin square

Cryptanalysis is important to the design of image cryptographic system. Recently, a two-round image cryptographic system is proposed and the authors claim that it is security. However, we find that the diffusion equation causes certain cipher images to appear period. According to this feature, we analyze one-round encryption by chosen-plaintext attack at first. And the encrypted image is successfully cracked. Then, we analyze two-round encryption in the same way. Although the encrypted image cannot be fully cracked, some equivalent keys are obtained. To remedy the loophole, the original encryption scheme is improved and the security analysis is performed. Experiments show that the improved cryptosystem can better resist chosen-plaintext attack while maintaining the same encryption performance as the original encryption scheme.