DES算法实现

概述(团队项目)

• DES是一个分组加密算法，它以64位为分组对数据加密。同时DES也是一个对称算法：加密和解密用的是同一个算法。DES是一个包含16个阶段的“替换–置换”的分组加密算法，64位的分组明文序列作为加密算法的输入，经过16轮加密得到64位的密文序列。

算法原理

• DES算法主要分为3部分：加解密运算、f函数的处理、轮子密钥的生成。

轮子密钥的生成

• 16个子密钥的生成主要是利用了数据表1中的数表，首先将64位的初始密钥利用PC1压缩置换位56位的密钥，然后将其一分为二，这里记为C0和D0。这里28位的C0和28位的D0分别根据LET数组相应位置的值进行左移位得到C1和D1。这是将C1和D1合并根据PC2进行压缩置换得到48位的子密钥，而且注意C1和D1作为下轮的输入以用来产生下一个子密钥。
  数据表1

 //PC-1
    private int[] PC1={57,49,41,33,25,17,9,
                       1,58,50,42,34,26,18,
                       10,2,59,51,43,35,27,
                        19,11,3,60,52,44,36,
                       63,55,47,39,31,23,15,
                       7,62,54,46,38,30,22,
                       14,6,61,53,45,37,29,
                       21,13,5,28,20,12,4};
    //PC-2
    private int[] PC2={14,17,11,24,1,5,3,28,
                       15,6,21,10,23,19,12,4,
                       26,8,16,7,27,20,13,2,
                       41,52,31,37,47,55,30,40,
                       51,45,33,48,44,49,39,56,
                       34,53,46,42,50,36,29,32};

    //Schedule of Left Shifts
    private int[] LFT={1,1,2,2,2,2,2,2,1,2,2,2,2,2,2,1};

f函数的运算

• 从原理图中可以看到，f函数的输入是明文分组的右半分组记为R和子密钥记为K。32位的R首先要利用数据表2中的E进行E盒扩展变换得到48位的数据，这里记为RE。然后将RE与K进行异或运算并将异或结果利用数据表2中的S_BOX进行S盒替换，得到48位的运算结果记为RS。再将RS利用数据表2中的P进行P盒替换，得到32位的最终结果，记为RF。到这里f函数的运算任务就完成了。
  数据表2

//E扩展
    private int[] E={32,1,2,3,4,5,
                      4,5,6,7,8,9,
                     8,9,10,11,12,13,
                     12,13,14,15,16,17,
                     16,17,18,19,20,21,
                     20,21,22,23,24,25,
                     24,25,26,27,28,29,
                     28,29,30,31,32,1};
    //P置换
    private int[] P={16,7,20,21,29,12,28,17,
                      1,15,23,26,5,18,31,10,
                      2,8,24,14,32,27,3,9,
                      19,13,30,6,22,11,4,25};

    private static final int[][][] S_Box = {//S-盒
            {// S_Box[1]
                    { 14, 4, 13, 1, 2, 15, 11, 8, 3, 10, 6, 12, 5, 9, 0, 7 },
                    { 0, 15, 7, 4, 14, 2, 13, 1, 10, 6, 12, 11, 9, 5, 3, 8 },
                    { 4, 1, 14, 8, 13, 6, 2, 11, 15, 12, 9, 7, 3, 10, 5, 0 },
                    { 15, 12, 8, 2, 4, 9, 1, 7, 5, 11, 3, 14, 10, 0, 6, 13 } },
            { // S_Box[2]
                    { 15, 1, 8, 14, 6, 11, 3, 4, 9, 7, 2, 13, 12, 0, 5, 10 },
                    { 3, 13, 4, 7, 15, 2, 8, 14, 12, 0, 1, 10, 6, 9, 11, 5 },
                    { 0, 14, 7, 11, 10, 4, 13, 1, 5, 8, 12, 6, 9, 3, 2, 15 },
                    { 13, 8, 10, 1, 3, 15, 4, 2, 11, 6, 7, 12, 0, 5, 14, 9 } },
            { // S_Box[3]
                    { 10, 0, 9, 14, 6, 3, 15, 5, 1, 13, 12, 7, 11, 4, 2, 8 },
                    { 13, 7, 0, 9, 3, 4, 6, 10, 2, 8, 5, 14, 12, 11, 15, 1 },
                    { 13, 6, 4, 9, 8, 15, 3, 0, 11, 1, 2, 12, 5, 10, 14, 7 },
                    { 1, 10, 13, 0, 6, 9, 8, 7, 4, 15, 14, 3, 11, 5, 2, 12 } },
            { // S_Box[4]
                    { 7, 13, 14, 3, 0, 6, 9, 10, 1, 2, 8, 5, 11, 12, 4, 15 },
                    { 13, 8, 11, 5, 6, 15, 0, 3, 4, 7, 2, 12, 1, 10, 14, 9 },
                    { 10, 6, 9, 0, 12, 11, 7, 13, 15, 1, 3, 14, 5, 2, 8, 4 },
                    { 3, 15, 0, 6, 10, 1, 13, 8, 9, 4, 5, 11, 12, 7, 2, 14 } },
            { // S_Box[5]
                    { 2, 12, 4, 1, 7, 10, 11, 6, 8, 5, 3, 15, 13, 0, 14, 9 },
                    { 14, 11, 2, 12, 4, 7, 13, 1, 5, 0, 15, 10, 3, 9, 8, 6 },
                    { 4, 2, 1, 11, 10, 13, 7, 8, 15, 9, 12, 5, 6, 3, 0, 14 },
                    { 11, 8, 12, 7, 1, 14, 2, 13, 6, 15, 0, 9, 10, 4, 5, 3 } },
            { // S_Box[6]
                    { 12, 1, 10, 15, 9, 2, 6, 8, 0, 13, 3, 4, 14, 7, 5, 11 },
                    { 10, 15, 4, 2, 7, 12, 9, 5, 6, 1, 13, 14, 0, 11, 3, 8 },
                    { 9, 14, 15, 5, 2, 8, 12, 3, 7, 0, 4, 10, 1, 13, 11, 6 },
                    { 4, 3, 2, 12, 9, 5, 15, 10, 11, 14, 1, 7, 6, 0, 8, 13 } },
            { // S_Box[7]
                    { 4, 11, 2, 14, 15, 0, 8, 13, 3, 12, 9, 7, 5, 10, 6, 1 },
                    { 13, 0, 11, 7, 4, 9, 1, 10, 14, 3, 5, 12, 2, 15, 8, 6 },
                    { 1, 4, 11, 13, 12, 3, 7, 14, 10, 15, 6, 8, 0, 5, 9, 2 },
                    { 6, 11, 13, 8, 1, 4, 10, 7, 9, 5, 0, 15, 14, 2, 3, 12 } },
            { // S_Box[8]
                    { 13, 2, 8, 4, 6, 15, 11, 1, 10, 9, 3, 14, 5, 0, 12, 7 },
                    { 1, 15, 13, 8, 10, 3, 7, 4, 12, 5, 6, 11, 0, 14, 9, 2 },
                    { 7, 11, 4, 1, 9, 12, 14, 2, 0, 6, 10, 13, 15, 3, 5, 8 },
                    { 2, 1, 14, 7, 4, 10, 8, 13, 15, 12, 9, 0, 3, 5, 6, 11 } }
    };

加解密运算

• 在第一轮中将64位的明文分为L0和R0,则加密运算如下：L1=R0 R1=L0⊕f(R0,K0) ,然后按此公式进行16轮的运算。

 //初始置换
    private int[] IP={58,50,42,34,26,18,10,2,
                     60,52,44,36,28,20,12,4,
                     62,54,46,38,30,22,14,6,
                     64,56,48,40,32,24,16,8,
                     57,49,41,33,25,17,9,1,
                     59,51,43,35,27,19,11,3,
                     61,53,45,37,29,21,13,5,
                     63,55,47,39,31,23,15,7};
    //逆初始置换
    private int[] IP_1={40,8,48,16,56,24,64,32,
                       39,7,47,15,55,23,63,31,
                       38,6,46,14,54,22,62,30,
                       37,5,45,13,53,21,61,29,
                       36,4,44,12,52,20,60,28,
                       35,3,43,11,51,19,59,27,
                       34,2,42,10,50,18,58,26,
                       33,1,41,9,49,17,57,25};

代码实现

package  DES算法;
public class DES {
    byte[] bytekey;
    public DES(String strKey) {
        this.bytekey = strKey.getBytes();
    }// 声明常量字节数组
    private static final int[] IP = { 58, 50, 42, 34, 26, 18, 10, 2, 60, 52,
            44, 36, 28, 20, 12, 4, 62, 54, 46, 38, 30, 22, 14, 6, 64, 56, 48,
            40, 32, 24, 16, 8, 57, 49, 41, 33, 25, 17, 9, 1, 59, 51, 43, 35,
            27, 19, 11, 3, 61, 53, 45, 37, 29, 21, 13, 5, 63, 55, 47, 39, 31,
            23, 15, 7 }; // 64
    private static final int[] IP_1 = { 40, 8, 48, 16, 56, 24, 64, 32, 39, 7,
            47, 15, 55, 23, 63, 31, 38, 6, 46, 14, 54, 22, 62, 30, 37, 5, 45,
            13, 53, 21, 61, 29, 36, 4, 44, 12, 52, 20, 60, 28, 35, 3, 43, 11,
            51, 19, 59, 27, 34, 2, 42, 10, 50, 18, 58, 26, 33, 1, 41, 9, 49,
            17, 57, 25 }; // 64
    private static final int[] PC_1 = { 57, 49, 41, 33, 25, 17, 9, 1, 58, 50,
            42, 34, 26, 18, 10, 2, 59, 51, 43, 35, 27, 19, 11, 3, 60, 52, 44,
            36, 63, 55, 47, 39, 31, 23, 15, 7, 62, 54, 46, 38, 30, 22, 14, 6,
            61, 53, 45, 37, 29, 21, 13, 5, 28, 20, 12, 4 }; // 56
    private static final int[] PC_2 = { 14, 17, 11, 24, 1, 5, 3, 28, 15, 6, 21,
            10, 23, 19, 12, 4, 26, 8, 16, 7, 27, 20, 13, 2, 41, 52, 31, 37, 47,
            55, 30, 40, 51, 45, 33, 48, 44, 49, 39, 56, 34, 53, 46, 42, 50, 36,
            29, 32 }; // 48
    private static final int[] E = { 32, 1, 2, 3, 4, 5, 4, 5, 6, 7, 8, 9, 8, 9,
            10, 11, 12, 13, 12, 13, 14, 15, 16, 17, 16, 17, 18, 19, 20, 21, 20,
            21, 22, 23, 24, 25, 24, 25, 26, 27, 28, 29, 28, 29, 30, 31, 32, 1 }; // 48
    private static final int[] P = { 16, 7, 20, 21, 29, 12, 28, 17, 1, 15, 23,
            26, 5, 18, 31, 10, 2, 8, 24, 14, 32, 27, 3, 9, 19, 13, 30, 6, 22,
            11, 4, 25 }; // 32
    private static final int[][][] S_Box = {//S-盒
            {// S_Box[1]
                    { 14, 4, 13, 1, 2, 15, 11, 8, 3, 10, 6, 12, 5, 9, 0, 7 },
                    { 0, 15, 7, 4, 14, 2, 13, 1, 10, 6, 12, 11, 9, 5, 3, 8 },
                    { 4, 1, 14, 8, 13, 6, 2, 11, 15, 12, 9, 7, 3, 10, 5, 0 },
                    { 15, 12, 8, 2, 4, 9, 1, 7, 5, 11, 3, 14, 10, 0, 6, 13 } },
            { // S_Box[2]
                    { 15, 1, 8, 14, 6, 11, 3, 4, 9, 7, 2, 13, 12, 0, 5, 10 },
                    { 3, 13, 4, 7, 15, 2, 8, 14, 12, 0, 1, 10, 6, 9, 11, 5 },
                    { 0, 14, 7, 11, 10, 4, 13, 1, 5, 8, 12, 6, 9, 3, 2, 15 },
                    { 13, 8, 10, 1, 3, 15, 4, 2, 11, 6, 7, 12, 0, 5, 14, 9 } },
            { // S_Box[3]
                    { 10, 0, 9, 14, 6, 3, 15, 5, 1, 13, 12, 7, 11, 4, 2, 8 },
                    { 13, 7, 0, 9, 3, 4, 6, 10, 2, 8, 5, 14, 12, 11, 15, 1 },
                    { 13, 6, 4, 9, 8, 15, 3, 0, 11, 1, 2, 12, 5, 10, 14, 7 },
                    { 1, 10, 13, 0, 6, 9, 8, 7, 4, 15, 14, 3, 11, 5, 2, 12 } },
            { // S_Box[4]
                    { 7, 13, 14, 3, 0, 6, 9, 10, 1, 2, 8, 5, 11, 12, 4, 15 },
                    { 13, 8, 11, 5, 6, 15, 0, 3, 4, 7, 2, 12, 1, 10, 14, 9 },
                    { 10, 6, 9, 0, 12, 11, 7, 13, 15, 1, 3, 14, 5, 2, 8, 4 },
                    { 3, 15, 0, 6, 10, 1, 13, 8, 9, 4, 5, 11, 12, 7, 2, 14 } },
            { // S_Box[5]
                    { 2, 12, 4, 1, 7, 10, 11, 6, 8, 5, 3, 15, 13, 0, 14, 9 },
                    { 14, 11, 2, 12, 4, 7, 13, 1, 5, 0, 15, 10, 3, 9, 8, 6 },
                    { 4, 2, 1, 11, 10, 13, 7, 8, 15, 9, 12, 5, 6, 3, 0, 14 },
                    { 11, 8, 12, 7, 1, 14, 2, 13, 6, 15, 0, 9, 10, 4, 5, 3 } },
            { // S_Box[6]
                    { 12, 1, 10, 15, 9, 2, 6, 8, 0, 13, 3, 4, 14, 7, 5, 11 },
                    { 10, 15, 4, 2, 7, 12, 9, 5, 6, 1, 13, 14, 0, 11, 3, 8 },
                    { 9, 14, 15, 5, 2, 8, 12, 3, 7, 0, 4, 10, 1, 13, 11, 6 },
                    { 4, 3, 2, 12, 9, 5, 15, 10, 11, 14, 1, 7, 6, 0, 8, 13 } },
            { // S_Box[7]
                    { 4, 11, 2, 14, 15, 0, 8, 13, 3, 12, 9, 7, 5, 10, 6, 1 },
                    { 13, 0, 11, 7, 4, 9, 1, 10, 14, 3, 5, 12, 2, 15, 8, 6 },
                    { 1, 4, 11, 13, 12, 3, 7, 14, 10, 15, 6, 8, 0, 5, 9, 2 },
                    { 6, 11, 13, 8, 1, 4, 10, 7, 9, 5, 0, 15, 14, 2, 3, 12 } },
            { // S_Box[8]
                    { 13, 2, 8, 4, 6, 15, 11, 1, 10, 9, 3, 14, 5, 0, 12, 7 },
                    { 1, 15, 13, 8, 10, 3, 7, 4, 12, 5, 6, 11, 0, 14, 9, 2 },
                    { 7, 11, 4, 1, 9, 12, 14, 2, 0, 6, 10, 13, 15, 3, 5, 8 },
                    { 2, 1, 14, 7, 4, 10, 8, 13, 15, 12, 9, 0, 3, 5, 6, 11 } }
    };
    private static final int[] LeftMove = { 1, 1, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2,2, 2, 2, 1 };
    // 左移位置列表
    private byte[] UnitDes(byte[] des_key, byte[] des_data, int flag) {
        // 检测输入参数格式是否正确，错误直接返回空值（null）
        if ((des_key.length != 8) || (des_data.length != 8)|| ((flag != 1) && (flag != 0))) {
            throw new RuntimeException("Data Format Error !");
        }
        int flags = flag;// 二进制加密密钥
        int[] keydata = new int[64];// 二进制加密数据
        int[] encryptdata = new int[64]; // 加密操作完成后的字节数组
        byte[] EncryptCode = new byte[8];// 密钥初试化成二维数组
        int[][] KeyArray = new int[16][48];// 将密钥字节数组转换成二进制字节数组
        keydata = ReadDataToBirnaryIntArray(des_key);// 将加密数据字节数组转换成二进制字节数组
        encryptdata = ReadDataToBirnaryIntArray(des_data);// 初试化密钥为二维密钥数组
        KeyInitialize(keydata, KeyArray); // 执行加密解密操作
        EncryptCode = Encrypt(encryptdata, flags, KeyArray);
        return EncryptCode;
    }// 初试化密钥数组
    private void KeyInitialize(int[] key, int[][] keyarray) {
        int i;
        int j;
        int[] K0 = new int[56];// 特别注意：xxx[IP[i]-1]等类似变换
        for (i = 0; i < 56; i++) {
            K0[i] = key[PC_1[i] - 1]; // 密钥进行PC-1变换
        }
        for (i = 0; i < 16; i++) {
            LeftBitMove(K0, LeftMove[i]); // 特别注意：xxx[IP[i]-1]等类似变换
            for (j = 0; j < 48; j++) {
                keyarray[i][j] = K0[PC_2[j] - 1]; // 生成子密钥keyarray[i][j]
            }
        }
    } // 执行加密解密操作
    private byte[] Encrypt(int[] timeData, int flag, int[][] keyarray) {
        int i;
        byte[] encrypt = new byte[8];
        int flags = flag;
        int[] M = new int[64];
        int[] MIP_1 = new int[64];
// 特别注意：xxx[IP[i]-1]等类似变换
        for (i = 0; i < 64; i++) {
            M[i] = timeData[IP[i] - 1]; // 明文IP变换
        }
        if (flags == 1) { // 加密
            for (i = 0; i < 16; i++) {
                LoopF(M, i, flags, keyarray);
            }
        } else if (flags == 0) { // 解密
            for (i = 15; i > -1; i--) {
                LoopF(M, i, flags, keyarray);
            }
        }
        for (i = 0; i < 64; i++) {
            MIP_1[i] = M[IP_1[i] - 1]; // 进行IP-1运算
        }
        GetEncryptResultOfByteArray(MIP_1, encrypt);// 返回加密数据
        return encrypt;
    }
    private int[] ReadDataToBirnaryIntArray(byte[] intdata) {
        int i;
        int j;
        // 将数据转换为二进制数，存储到数组
        int[] IntDa = new int[8];
        for (i = 0; i < 8; i++) {
            IntDa[i] = intdata[i];
            if (IntDa[i] < 0) {
                IntDa[i] += 256;
                IntDa[i] %= 256;
            }
        }
        int[] IntVa = new int[64];
        for (i = 0; i < 8; i++) {
            for (j = 0; j < 8; j++) {
                IntVa[((i * 8) + 7) - j] = IntDa[i] % 2;
                IntDa[i] = IntDa[i] / 2;
            }
        }
        return IntVa;
    }
    private void LeftBitMove(int[] k, int offset) {
        int i;
        // 循环移位操作函数
        int[] c0 = new int[28];
        int[] d0 = new int[28];
        int[] c1 = new int[28];
        int[] d1 = new int[28];
        for (i = 0; i < 28; i++) {
            c0[i] = k[i];
            d0[i] = k[i + 28];
        }
        if (offset == 1) {
            for (i = 0; i < 27; i++) { // 循环左移一位
                c1[i] = c0[i + 1];
                d1[i] = d0[i + 1];
            }
            c1[27] = c0[0];
            d1[27] = d0[0];
        } else if (offset == 2) {
            for (i = 0; i < 26; i++) { // 循环左移两位
                c1[i] = c0[i + 2];
                d1[i] = d0[i + 2];
            }
            c1[26] = c0[0];
            d1[26] = d0[0];
            c1[27] = c0[1];
            d1[27] = d0[1];
        }
        for (i = 0; i < 28; i++) {
            k[i] = c1[i];
            k[i + 28] = d1[i];
        }
    }
    private void LoopF(int[] M, int times, int flag, int[][] keyarray) {
        int i;
        int j;
        int[] L0 = new int[32];
        int[] R0 = new int[32];
        int[] L1 = new int[32];
        int[] R1 = new int[32];
        int[] RE = new int[48];
        int[][] S = new int[8][6];
        int[] sBoxData = new int[8];
        int[] sValue = new int[32];
        int[] RP = new int[32];
        for (i = 0; i < 32; i++) {
            L0[i] = M[i]; // 明文左侧的初始化
            R0[i] = M[i + 32]; // 明文右侧的初始化
        }
        for (i = 0; i < 48; i++) {
            RE[i] = R0[E[i] - 1]; // 经过E变换扩充，由32位变为48位
            RE[i] = RE[i] + keyarray[times][i]; // 与KeyArray[times][i]按位作不进位加法运算
            if (RE[i] == 2) {
                RE[i] = 0;
            }
        }
        for (i = 0; i < 8; i++) { // 48位分成8组
            for (j = 0; j < 6; j++) {
                S[i][j] = RE[(i * 6) + j];
            }
            // 下面经过S盒，得到8个数
            sBoxData[i] = S_Box[i][(S[i][0] << 1) + S[i][5]][(S[i][1] << 3)
                    + (S[i][2] << 2) + (S[i][3] << 1) + S[i][4]];
            // 8个数变换输出二进制
            for (j = 0; j < 4; j++) {
                sValue[((i * 4) + 3) - j] = sBoxData[i] % 2;
                sBoxData[i] = sBoxData[i] / 2;
            }
        }
        for (i = 0; i < 32; i++) {
            RP[i] = sValue[P[i] - 1]; // 经过P变换
            L1[i] = R0[i]; // 右边移到左边
            R1[i] = L0[i] + RP[i];
            if (R1[i] == 2) {
                R1[i] = 0;
            }
            // 重新合成M，返回数组M
            // 最后一次变换时，左右不进行互换。此处采用两次变换实现不变
            if (((flag == 0) && (times == 0)) || ((flag == 1) && (times == 15))) {
                M[i] = R1[i];
                M[i + 32] = L1[i];
            }
            else {
                M[i] = L1[i];
                M[i + 32] = R1[i];
            }
        }
    }
    private void GetEncryptResultOfByteArray(int[] data, byte[] value) {
        int i;
        int j; // 将存储64位二进制数据的数组中的数据转换为八个整数（byte）
        for (i = 0; i < 8; i++) {
            for (j = 0; j < 8; j++) {
                value[i] += (data[(i << 3) + j] << (7 - j));
            }
        }
        for (i = 0; i < 8; i++) {
            value[i] %= 256;
            if (value[i] > 128) {
                value[i] -= 255;
            }
        }
    }
    private byte[] ByteDataFormat(byte[] data, int flag) {
        int len = data.length;
        int padlen = 8 - (len % 8);
        int newlen = len + padlen;
        byte[] newdata = new byte[newlen];
        System.arraycopy(data, 0, newdata, 0, len);
        for (int i = len; i < newlen; i++)
            newdata[i] = (byte) padlen;
        return newdata;
    }
    public byte[] DesEncrypt(byte[] des_data, int flag) {
        byte[] format_key = ByteDataFormat(bytekey, flag);
        byte[] format_data = ByteDataFormat(des_data, flag);
        int datalen = format_data.length;
        int unitcount = datalen / 8;
        byte[] result_data = new byte[datalen];
        for (int i = 0; i < unitcount; i++) {
            byte[] tmpkey = new byte[8];
            byte[] tmpdata = new byte[8];
            System.arraycopy(format_key, 0, tmpkey, 0, 8);
            System.arraycopy(format_data, i * 8, tmpdata, 0, 8);
            byte[] tmpresult = UnitDes(tmpkey, tmpdata, flag);
            System.arraycopy(tmpresult, 0, result_data, i * 8, 8);
        } // 当前为解密过程，去掉加密时产生的填充位
        byte[] decryptbytearray = null;
        if (flag == 0) {
            int total_len = datalen;
            int delete_len = result_data[total_len - 8 - 1];
            delete_len = ((delete_len >= 1) && (delete_len <= 8)) ? delete_len : 0;
            decryptbytearray = new byte[total_len - delete_len - 8];
            boolean del_flag = true;
            for (int k = 0; k < delete_len; k++) {
                if (delete_len != result_data[total_len - 8 - (k + 1)])
                    del_flag = false;
            }
            if (del_flag == true) {
                System.arraycopy(result_data, 0, decryptbytearray, 0, total_len- delete_len - 8);
            }
        }
        return (flag == 1) ? result_data : decryptbytearray;
    }
    public static void main(String[] args) {
        String key = "这是密钥";
        String data = "wpy是沙雕";
        DES desUtil = new DES(key);
        System.err.println("加密前明文：" + data);
        // 加密后的byte型的密文
        byte[] result = desUtil.DesEncrypt(data.getBytes(), 1);
        System.err.println("加密后密文：" + new String(result));
        // 下句直接把byte类型的密文解密
        System.err.println("解密后明文："+ new String(desUtil.DesEncrypt(result, 0)));
    }
}

代码更改

更改要求

• 1.在项目初步设计时，我们需要将加解密的明密文进行，文件操作，即将明密文文件读入在加解密后保存至指定文件夹
• 2.同时需要进行功能选择，进行加密或解密其中一项

更改主函数代码实现

 public static void main(String[] args) {
        Scanner inn = new Scanner(System.in);
        System.out.println("请选择你想要执行的任务：
1.加密明文;
2.解密密文");
        int choose = inn.nextInt();
        if(choose == 1){
            System.out.println("请输入保存明文的文件名：");
            String MFile = inn.next();
            System.out.println("请输入加解密所需密钥：");
            String key = inn.next();
            String data = "";
            int n=-1;
            byte [] a=new byte[100];
            try{  File f=new File(MFile);
                InputStream in = new FileInputStream(f);
                while((n=in.read(a,0,100))!=-1) {
                    data=new String (a,0,n);
                }
                in.close();
            }
            catch(IOException e) {
                System.out.println("File read Error"+e);
            }
            DES desUtil = new DES(key);
            System.err.println("加密前明文：" + data);
            // 加密后的byte型的密文
            byte[] result = desUtil.DesEncrypt(data.getBytes(), 1);
            System.err.println("加密后密文：" + new String(result));
            System.out.println("请输入保存密文的文件名：");
            String MMFile = inn.next();
            // 下句直接把byte类型的密文解密
            File file = new File(MMFile);
            try{
                OutputStream out=new FileOutputStream(file);
                out.write(result);
                out.close();
                out=new FileOutputStream(file,true);
            }
            catch(IOException e) {
                System.out.println("Error "+e);
            }
        }
       else if(choose == 2){
            System.out.println("请输入保存密文的文件名：");
            String MFile = inn.next();
            System.out.println("请输入加解密所需密钥：");
            String key = inn.next();
            String result = "";
            int n=-1;
            byte [] a=new byte[100];
            try{  File f=new File(MFile);
                InputStream in = new FileInputStream(f);
                while((n=in.read(a,0,100))!=-1) {
                    result=new String (a,0,n);
                }
                in.close();
            }
            catch(IOException e) {
                System.out.println("File read Error"+e);
            }
            DES desUtil = new DES(key);
            System.err.println("解密前密文：" + result);
            byte [] data = desUtil.DesEncrypt(result.getBytes(), 0);
            System.err.println("解密后明文："+  desUtil.DesEncrypt(result.getBytes(), 0));
            System.out.println("请输入保存明文的文件名：");
            String MMFile = inn.next();
            File file = new File(MMFile);
            try{
                OutputStream out=new FileOutputStream(file);
                out.write(data);
                out.close();
                out=new FileOutputStream(file,true);
            }
            catch(IOException e) {
                System.out.println("Error "+e);
            }
        }

    }

预览截图

• 施行加密
  

• 施行解密
  

遇到还未解决的问题

• DES在更改后解密时由于密文字符读入的问题发生偏差，导致解密后的明文Byte数组出现偏差，目前正在找方法解决。

参考资料