基于SMS4分组密码的彩色图像加密方法

为实现对数字彩色图像信息的有效保护,提出了一种采用SMS4分组加密的彩色图像加密方法。首先使用变参数的Arnold变换对图像进行位置置乱,其次使用外部密钥控制Logistic混沌映射产生各个SMS4分组的主密钥MK,以及任取32bit的随机整数作为加密子密钥并赋值给第1个SMS4分组加密图像的低32bit输入;再次分别将每个SMS4分组加密图像的低32bit输出作为下一个分组图像加密的低32bit输入,使得SMS4分组加密与反馈流密码相结合;最后将最后一组SMS4分组加密图像的低32bit输出作为图像解密的子密钥。加解密钥并不完全相同且解密子密钥与明文、密文紧密相关。实验结果表明,该方法具有良好的雪崩效应,可有效抵抗统计、差分和选择性明文等攻击。

A color image block encryption algorithm based on SMS4

In order to protect digital color image＇s information, a color image encryption method based on SMS4 block encryption is proposed. Firstly, the image is scrambled by means of the variable-parameters Arnold transform. Secondly, the main key MK of every SMS4 block image is generated by combining the logistic mapping with external keys and a 32bit random number is selected as the encryption sub key which is assigned to the low 32bit input of the first SMS4 block. Thirdly, take the low 32bit output of every SMS4 block image as the low 32bit input of the next block image respectively to make the SMS4 block encryption and feedback flow password combined. Finally, the decryption sub key is generated by taking the low 32bit output of the last SMS4 block. Decryption keys, which have a close relationship with the encryption image and the original image, are incomplete identical with encryption keys. Experimental results show that, the proposed algorithm is with the avalanche effect, it can effectively resist statistical attack, differential attack and chosen-plaintext attack.