DES

/*
2015.4
DES加解密类
*/
#ifndef DES_H
#define DES_H

#include <iostream>  
#include <string>
#include <bitset>    
using namespace std;

class DES
{
public:
    void GetKey(char k[8]);
    //生成16个子密钥
    void generateKeys();

    void encrypt(const char input[8], char output[8]);
    void decrypt(const char input[8], char output[8]);

    void StrEncrypt(string plaintext, string &ciphertext);
    void StrDecrypt(string ciphertext, string &output);

private:
    bitset<64> key;                // 64位密钥  
    bitset<48> subKey[16];         // K1~K16子密钥 
    bitset<64> plain;
    bitset<64> cipher;

    bitset<64> charToBitset(const char s[8]);
    void bitToChar(bitset<64> bits, char c[8]);

    //圈函数
    bitset<32> f(bitset<32> R, bitset<48> k);
    bitset<28> leftShift(bitset<28> k, int shift);

};

#endif

#include "DES.h"

//IP置换表  
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 };

//IP-1置换表  
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 };

//将64位密钥变成56位  
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 };

//将56位密钥压缩成48位子密钥  
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 };

//每轮左移的位数  
int shiftBits[] = { 1, 1, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 1 };

//E置换表，将32位扩展至48位  
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 };

//S盒 4x16 
int S_BOX[8][4][16] = {
    {
        { 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 }
    },
    {
        { 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 }
    },
    {
        { 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 }
    },
    {
        { 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 }
    },
    {
        { 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 }
    },
    {
        { 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 }
    },
    {
        { 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 }
    },
    {
        { 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 }
    }
};

//P置换
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 };


//密码函数f，接收32位数据和48位子密钥，产生一个32位的输出
bitset<32> DES::f(bitset<32> R, bitset<48> k)
{
    bitset<48> expandR;
    //E 
    for (int i = 0; i<48; ++i)
        expandR[47 - i] = R[32 - E[i]];
    //异或  
    expandR = expandR ^ k;
    //查找S_BOX 
    bitset<32> output;
    int x = 0;
    //48 bit分为8组
    for (int i = 0; i<48; i = i + 6)
    {
        // i = x1x6 + 1 
        int row = expandR[47 - i] * 2 + expandR[47 - i - 5];
        // j = x2x3x4x5 + 1
        int col = expandR[47 - i - 1] * 8 + expandR[47 - i - 2] * 4 + expandR[47 - i - 3] * 2 + expandR[47 - i - 4];
        //每个S-盒
        int num = S_BOX[i / 6][row][col];
        //转化为bit
        bitset<4> binary(num);
        output[31 - x] = binary[3];
        output[31 - x - 1] = binary[2];
        output[31 - x - 2] = binary[1];
        output[31 - x - 3] = binary[0];
        x += 4;
    }
    //P置换
    bitset<32> tmp = output;
    for (int i = 0; i<32; ++i)
        output[31 - i] = tmp[32 - P[i]];
    return output;
}

//对56位密钥的前后部分进行左移
bitset<28> DES::leftShift(bitset<28> k, int shift)
{
    bitset<28> tmp = k;
    for (int i = 27; i >= 0; --i)
    {
        if (i - shift<0)
            k[i] = tmp[i - shift + 28];
        else
            k[i] = tmp[i - shift];
    }
    return k;
}

void DES::GetKey(char k[8])
{
    key = charToBitset(k);
}

//将char字符数组转为二进制
bitset<64> DES::charToBitset(const char s[8])
{
    bitset<64> bits;
    for (unsigned i = 0; i < 8; ++i)
    for (unsigned j = 0; j < 8; ++j)
        bits[i * 8 + j] = ((s[i] >> j) & 1);
    return bits;
}

//将二进制转为char字符数组
void DES::bitToChar(bitset<64> bits, char c[8])
{
    for (int j = 0; j < 8; j++)
        c[j] = 0;
    for (unsigned i = 0; i < 64; i++)
    {
        if (bits.test(i))    //该位是否为1
            c[i / 8] |= 1 << (i % 8);
    }
}

//生成16个子密钥
void DES::generateKeys()
{
    bitset<56> realKey;
    bitset<28> left;
    bitset<28> right;
    bitset<48> compressKey;

    // 去掉奇偶标记位，将64位密钥变成56位  
    for (int i = 0; i<56; ++i)
        realKey[55 - i] = key[64 - PC_1[i]];
    // 生成子密钥，保存在 subKeys[16] 中  
    for (int round = 0; round<16; ++round)
    {
        // 前28位与后28位  
        for (int i = 28; i<56; ++i)
            left[i - 28] = realKey[i];
        for (int i = 0; i<28; ++i)
            right[i] = realKey[i];
        // 左移  
        left = leftShift(left, shiftBits[round]);
        right = leftShift(right, shiftBits[round]);
        // 压缩置换，由56位得到48位子密钥  
        for (int i = 28; i<56; ++i)
            realKey[i] = left[i - 28];
        for (int i = 0; i<28; ++i)
            realKey[i] = right[i];
        for (int i = 0; i<48; ++i)
            compressKey[47 - i] = realKey[56 - PC_2[i]];
        subKey[round] = compressKey;
    }
    /*cout << endl << "16个子密钥：" << endl;
    for (int i = 0; i < 16; i++)
    {
        cout << subKey[i] << endl;
    }
    cout << endl;*/
}

//DES加密
void DES::encrypt(const char input[8], char output[8])
{
    bitset<64> currentBits;
    bitset<32> left;
    bitset<32> right;
    bitset<32> newLeft;

    plain = charToBitset(input);
    //初始置换IP  
    for (int i = 0; i<64; ++i)
        currentBits[63 - i] = plain[64 - IP[i]];
    //获取 Li 和 Ri  
    for (int i = 32; i<64; ++i)
        left[i - 32] = currentBits[i];
    for (int i = 0; i<32; ++i)
        right[i] = currentBits[i];
    //16轮迭代  
    for (int round = 0; round<16; ++round)
    {
        newLeft = right;
        right = left ^ f(right, subKey[round]);
        left = newLeft;
    }
    //合并L16和R16,合并为R16L16   
    for (int i = 0; i<32; ++i)
        cipher[i] = left[i];
    for (int i = 32; i<64; ++i)
        cipher[i] = right[i - 32];
    //尾置换IP-1  
    currentBits = cipher;
    for (int i = 0; i<64; ++i)
        cipher[63 - i] = currentBits[64 - IP_1[i]];

    bitToChar(cipher, output);
    /*cout << "得到密文:" ;
    for (int i = 0; i < 8; i++)
        cout << output[i] << endl;*/
}
//DES解密
void DES::decrypt(const char input[8], char output[8])
{
    bitset<64> currentBits;
    bitset<32> left;
    bitset<32> right;
    bitset<32> newLeft;

    cipher = charToBitset(input);
    //初始置换IP  
    for (int i = 0; i<64; ++i)
        currentBits[63 - i] = cipher[64 - IP[i]];
    //获取 Li 和 Ri  
    for (int i = 32; i<64; ++i)
        left[i - 32] = currentBits[i];
    for (int i = 0; i<32; ++i)
        right[i] = currentBits[i];
    //共16轮迭代（子密钥逆序应用）  
    for (int round = 0; round<16; ++round)
    {
        newLeft = right;
        right = left ^ f(right, subKey[15 - round]);
        left = newLeft;
    }
    //合并L16和R16,合并为R16L16  
    for (int i = 0; i<32; ++i)
        plain[i] = left[i];
    for (int i = 32; i<64; ++i)
        plain[i] = right[i - 32];
    //尾置换IP-1  
    currentBits = plain;
    for (int i = 0; i<64; ++i)
        plain[63 - i] = currentBits[64 - IP_1[i]];
 
    bitToChar(plain, output);
    /*cout << "得到密文解:";
    for (int i = 0; i < 8; i++)
        cout << output[i] << endl;*/
}

//string任意长明文加密
void DES::StrEncrypt(string plaintext, string &ciphertext)
{
    char output[8];
    string stradd = "        ";
    string per = output;
    int length = plaintext.length();
    if (length % 8 != 0)
    {//明文不是8的倍数，用空格填充
        plaintext.append(stradd, 0, 8 - length % 8);
    }
    length = plaintext.length();
    for (int i = 0; i < length; i += 8)
    {
        per = plaintext.substr(i, 8);
        encrypt(per.c_str(),output);
        per = output;
        ciphertext += per.substr(0,8);
    }
}

//string任意长密文解密
void DES::StrDecrypt(string ciphertext, string &output)
{
    char out[8];
    string per = out;
    int length = ciphertext.length();
    for (int i = 0; i < length; i += 8)
    {
        per = ciphertext.substr(i, 8);
        decrypt(per.c_str(), out);
        per = out;
        output += per.substr(0,8);
    }
}

#include <iostream>   
#include <string>
#include "DES.h"
using namespace std;


int main()
{
    DES des;
    char key[8];
    string k;
    string plaintext, ciphertext, output;
    
    cout << "输入明文： ";
    cin >> plaintext;
    cout << "输入密钥： ";
    for (int i = 0; i < 8; i++)
        cin >> key[i];
    des.GetKey(key);
    des.generateKeys();    

    des.StrEncrypt(plaintext, ciphertext);
    cout << endl << "输出密文： " << ciphertext.c_str() << endl;
    des.StrDecrypt(ciphertext, output);
    cout << endl << "解密密文： " << output.c_str() << endl;

    cout << endl;
    return 0;
}