中文说明：加密阶段的这两个过程都存在弱点，在不知道密钥值的情况下，可以通过选择明文攻击和选择密文攻击来恢复加密后的图像。它只需要三对明文/密文就可以完全破坏密码系统。
English Description：
These two processes in the encryption stage present weakness, and a chosen plaintext attack and a chosen ciphertext attack can be done to recover the ciphered-image without any knowledge of the key value. It just demands three couples of plaintext/ciphertext to break totally the cryptosystem.