【java】DES算法加解密原理 （完全用代码还原DES，非导包）

一、DES原理介绍

DES加密算法（带示例）
DES算法原理完整版

二、DES实验结果

三、DES源码

源代码里有很多很多注释了，仔细研究一下，就能搞懂了。

public class DESwanmao {
    byte[] bytekey;
    public DESwanmao(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 逆初始置换表
    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[] LeftMove = { 1, 1, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2,2, 2, 2, 1 };// 循环移位表、用于子密钥的左移
    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，8个S变换表。
            {// 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 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("数据格式化失败！Data Format Error!");
        }
        int flags = flag;//加解密的标识，1代表进行加密操作，0代表进行解密操作
        int[] keydata = new int[64];// 二进制加密密钥
        int[] encryptdata = new int[64]; // 二进制加密数据
        byte[] EncryptCode = new byte[8];// 加密操作完成后的字节数组
        int[][] KeyArray = new int[16][48];// 密钥初试化成二维数组
        keydata = ReadDataToBirnaryIntArray(des_key);// 将密钥字节数组转换成二进制字节数组
        encryptdata = ReadDataToBirnaryIntArray(des_data);// 将加密数据字节数组转换成二进制字节数组
        KeyInitialize(keydata, KeyArray); // 初试化密钥为二维密钥数组
        EncryptCode = Encrypt(encryptdata, flags, KeyArray);// 执行加密解密操作
        return EncryptCode;//返回操作完成后字节数组
    }
    /*****初试化密钥数组，并存储在变量keyarray[i][j]中*****/
    private void KeyInitialize(int[] key, int[][] keyarray) {
        int i, j;
        int[] K0 = new int[56];
        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]);//按轮次对子密钥进行数据左移
            for (j = 0; j < 48; j++) {
                keyarray[i][j] = K0[PC_2[j] - 1]; //进行PC2变换生成生成子密钥keyarray[i][j]
            }
        }
    }
    /*****子密钥左移，根据循环移位表****/
    private void LeftBitMove(int[] k, int offset) {
        int i;
        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++) {//将56位数据平分成两组28位cO和cO
            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++) {//将做完数据左移后的左右两组28位数据c1和d1合并
            k[i] = c1[i];
            k[i + 28] = d1[i];
        }
    }
    /***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];//存放初始变换后的64位数据
        int[] MIP_1 = new int[64];//存放逆初始变换后的64位数据
        for (i = 0; i < 64; i++) {
            M[i] = timeData[IP[i] - 1]; // 明文IP初始变换，物理索引=逻辑索引-1
        }
        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]; // 进行逆初始置换IP-1运算
        }
        GetEncryptResultOfByteArray(MIP_1, encrypt);// 将64位数据转换为8位字节
        return encrypt;
    }
    /****将数据转换为二进制数，存储到字节数组****/
    private int[] ReadDataToBirnaryIntArray(byte[] intdata) {
        int i;
        int j;
        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;
    }
    /***f函数，包括E变换、与子密钥异或、S盒压缩、P变换***/
    private void LoopF(int[] M, int times, int flag, int[][] keyarray) {
        int i, 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];//存放根据循环变换表将输入数据的第n位
        int[][] S = new int[8][6];
        int[] sBoxData = new int[8];//存放经过S盒变换输出数据（8位
        int[] sValue = new int[32];//存放经过S盒变换输出数据的二进制形式（32位）
        int[] RP = new int[32];
        for (i = 0; i < 32; i++) {//将64位明文分为左右32位的两组数据
            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++) {// 经过E变换扩充，由32位变为48位
            RE[i] = R0[E[i] - 1]; //存放经过E变换后的数据
            RE[i] = RE[i] + keyarray[times][i]; // 经过E变换后的数据与子密钥KeyArray[times][i]按位作不进位加法运算
            if (RE[i] == 2 || RE[i] == 0) {//异或规则，当两个相等的数异或时结果为0时，它们的算术和为2或0.
                RE[i] = 0;
            }
        }
        for (i = 0; i < 8; i++) { //S盒变换： 将48位数据分成8组，每组6位
            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]];
            for (j = 0; j < 4; j++) {// 8个数变换输出为二进制
                sValue[((i * 4) + 3) - j] = sBoxData[i] % 2;
                sBoxData[i] = sBoxData[i] / 2;
            }
        }
        for (i = 0; i < 32; i++) {// P变换:将S盒输出的32位数据作为参数输入进行P变换，P[]是循环移位表
            RP[i] = sValue[P[i] - 1];//RP[i]存放根据循环变换表将输入数据的第n位
            L1[i] = R0[i]; // 右边移到左边
            R1[i] = L0[i] + RP[i];//异或操作： L0[i]与RP[i]按位作不进位加法运算得到R1
            if (R1[i] == 2 || R1[i] == 0) {//异或规则，当两个相等的数异或时结果为0时，它们的算术和为2或0.
                R1[i] = 0;
            }
            // 将左右32位数据组L和R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];
            }
        }
    }
    /***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）****/
    private void GetEncryptResultOfByteArray(int[] data, byte[] value) {
        int i, j;
        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;
            }
        }
    }
    /***格式化，不足8位倍数字节的补充***/
    private byte[] ByteDataFormat(byte[] data, int flag) {
        int len = data.length;
        int padlen = 8 - (len % 8);//算出缺多少位到8的倍数
        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;
    }

    /***加解密的控制流程操作，调用别的方法进行***/
    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++) {//加密过程，分组成8个字节一组进行加密，最后再合并
            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);//调用UnitDes方法进行
            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);
            }
        }
        //用来输出密文和解密后明文的ascii码组，flag为1时输出密文ascii码组，为0时输出解密后明文ascii码组
        String Bitstream_data="";
        if (flag==1){
            for (int i = 0; i < result_data.length; i++) {
                Bitstream_data += String.valueOf(result_data[i]);
            }
            String regEx="[-]";
            String a="";
            Bitstream_data=Bitstream_data.replaceAll(regEx,a);
            System.out.println("密文码组："+Bitstream_data);
        }else if (flag==0){
            for (int i = 0; i < decryptbytearray.length; i++) {
                Bitstream_data += String.valueOf(decryptbytearray[i]);
            }
            System.out.println("解密后的明文码组:"+Bitstream_data);
        }
        return (flag == 1) ? result_data : decryptbytearray;
    }
    public static void main(String[] args) {
        String key = "69875324";//密钥
        String data = "kenmiles";
        String spiltdata = "________________________";//分隔符
        DESwanmao deswanmao = new DESwanmao(key);//初始化
        byte[] dataBytes= data.getBytes();
        String original_data_Bitstream="";
        for (int i = 0; i < dataBytes.length; i++) {
            original_data_Bitstream += String.valueOf(dataBytes[i]);
        }
        System.out.println("原明文的码组："+original_data_Bitstream);
        System.out.println("加密前明文：\n" + data+"\n"+spiltdata);
        // 加密后的byte型的密文
        byte[] result = deswanmao.DesEncrypt(data.getBytes(), 1);
        System.out.println("加密后密文：\n" + new String(result)+"\n"+spiltdata);
        System.out.println("解密后明文：\n"+ new String(deswanmao.DesEncrypt(result, 0)));// 直接把byte类型的密文解密
    }
}