注意程序的第一句，此处不能对表达式作0xFF的与操作，否则运行结果不对，这里是于很难理解。笔者认为，从input[0] ^ n_LocKeyExpandBox[16 * m_nChipherLen]本身来讲，其结果经强制类型转换成byte后就已经保证了结果的高位为零，从而满足模256运算的需要。

最后将input置入输出数组output中，同样，与明文m_sInClearText置入byte型的字节数组input中相似，output数组的偶数位下标，即output[0]、output[2]、……、output[30]中均为密文数据，而奇数位下标，即output[1]，output[3]，……，output[31]均为0,从而保证byte型数组能转换成string型密文m_sCryptedText。

4．解密算法

该算法其实就是简单地将加密操作逆向进行，首先进行初始变换，即加密算法输出变换的逆向操作，因为对于模256“-”运算，其结果有可能小于0，因而此处要采用三目运算符 ？：来进行表达式结果判断，例如对input[2]而言，若input[2] - n_LocKeyExpandBox[16 * m_nChipherLen + 1]大于等于零，则结果为其自身，否则应将二者之差加上256，然后将整个结果与0xFF做与（&）操作，从而保证模256“-”运算的正确性，代码如下：

input[0] = (byte)((input[0] ^ n_LocKeyExpandBox[16 * m_nChipherLen]) & 0xFF);

                input[2] = (byte)(((input[2] - n_LocKeyExpandBox[16 * m_nChipherLen + 1]) >= 0 ? (input[2] - n_LocKeyExpandBox[16 * m_nChipherLen + 1]) : (input[2] - n_LocKeyExpandBox[16 * m_nChipherLen + 1] + 256)) & 0xFF);

                input[4] = (byte)(((input[4] - n_LocKeyExpandBox[16 * m_nChipherLen + 2]) >= 0 ? (input[4] - n_LocKeyExpandBox[16 * m_nChipherLen + 2]) : (input[4] - n_LocKeyExpandBox[16 * m_nChipherLen + 2] + 256)) & 0xFF);

               input[6] = (byte)((input[6] ^ n_LocKeyExpandBox[16 * m_nChipherLen + 3]) & 0xFF);

input[8] = (byte)((input[8] ^ n_LocKeyExpandBox[16 * m_nChipherLen + 4]) & 0xFF);

 input[10] = (byte)(((input[10] - n_LocKeyExpandBox[16 * m_nChipherLen + 5]) >= 0 ? (input[10] - n_LocKeyExpandBox[16 * m_nChipherLen + 5]) : (input[10] - n_LocKeyExpandBox[16 * m_nChipherLen + 5] + 256)) & 0xFF);

                input[12] = (byte)(((input[12] - n_LocKeyExpandBox[16 * m_nChipherLen + 6]) >= 0 ? (input[12] - n_LocKeyExpandBox[16 * m_nChipherLen + 6]) : (input[12] - n_LocKeyExpandBox[16 * m_nChipherLen + 6] + 256)) & 0xFF);

                input[14] = (byte)((input[14] ^ n_LocKeyExpandBox[16 * m_nChipherLen + 7]) & 0xFF);

input[16] = (byte)((input[16] ^ n_LocKeyExpandBox[16 * m_nChipherLen + 8]) & 0xFF);

input[18] = (byte)(((input[18] - n_LocKeyExpandBox[16 * m_nChipherLen + 9]) >= 0 ? (input[18] - n_LocKeyExpandBox[16 * m_nChipherLen + 9]) : (input[18] - n_LocKeyExpandBox[16 * m_nChipherLen + 9] + 256)) & 0xFF);

                input[20] = (byte)(((input[20] - n_LocKeyExpandBox[16 * m_nChipherLen + 10]) >= 0 ? (input[20] - n_LocKeyExpandBox[16 * m_nChipherLen + 10]) : (input[20] - n_LocKeyExpandBox[16 * m_nChipherLen + 10] + 256)) & 0xFF);

                input[22] = (byte)((input[22] ^ n_LocKeyExpandBox[16 * m_nChipherLen + 11]) & 0xFF);

input[24] = (byte)((input[24] ^ n_LocKeyExpandBox[16 * m_nChipherLen + 12]) & 0xFF);

input[26] = (byte)(((input[26] - n_LocKeyExpandBox[16 * m_nChipherLen + 13]) >= 0 ? (input[26] - n_LocKeyExpandBox[16 * m_nChipherLen + 13]) : (input[26] - n_LocKeyExpandBox[16 * m_nChipherLen + 13] + 256)) & 0xFF);

                input[28] = (byte)(((input[28] - n_LocKeyExpandBox[16 * m_nChipherLen + 14]) >= 0 ? (input[28] - n_LocKeyExpandBox[16 * m_nChipherLen + 14]) : (input[28] - n_LocKeyExpandBox[16 * m_nChipherLen + 14] + 256)) & 0xFF);

                input[30] = (byte)((input[30] ^ n_LocKeyExpandBox[16 * m_nChipherLen + 15]) & 0xFF);