DES加密算法详解

在网上搜了一下关于DES的说明，发现有些杂乱，所以还是有必要整合一下。

写了一点代码，还没有完成，不过，还不能编译通过，^_^

刚看了一下，发现还是说得够模糊的，有机会再整理一下。

昏倒，一直运行不对，今天才仔细查出来，原来问题是出在Des_Data_P(const _b32& input, _b32 output),

我的output用了传值调用，失败呀。应该是Des_Data_P(const _b32& input, _b32& output)

DES算法的入口参数有三个：
 Key, Data, Mode

Key 为64bit密钥， Data为64bit数据，Mode为加密还是解密。

DES算法的过程:

1. 对输入的密钥进行变换。
    用户的64bit密钥，其中第8， 16， 24， 32， 40， 48， 56， 64位是校验位， 使得每个密钥都有奇数个1。所以密钥事实上是56位。对这56位密钥进行如下表的换位。

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,

表的意思是第57位移到第1位，第49位移到第2位，...... 以此类推。变换后得到56bit数据，将它分成两部分，C[0][28], D[0][28]。

2. 计算16个子密钥，计算方法C[i][28] D[i][28]为对前一个C[i-1][28], D[i-1][28]做循环左移操作。16次的左移位数如下表:

 1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14, 15, 16   （第i次)
 1,  1,  2,  2,  2,  2,  2,  2,  1,   2,  2,   2,   2,   2,   2,  1    (左移位数)

3. 串联计算出来的C[i][28] D[i][28] 得到56位，然后对它进行如下变换得到48位子密钥K[i][48]

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,

表的意思是第14位移到第1位，第17位移到第2位，以此类推。在此过程中，发现第9，18，22，25， 35，38，43，54位丢弃。

4. 对64bit的明文输入进行换位变换。换位表如下:

58, 50, 12, 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

表的意思就是第一次变换时，第58位移到第1位，第50位移到第2位，...... 依此类推。得到64位数据，将这数据前后分成两块L[0][32], R[0][32]。

5. 加密过程，对R[i][32]进行扩展变换成48位数，方法如下， 记为E(R[i][32])

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,

6. 将E(R[i][32])与K[i][48]作异或运算，得到48位数，将48位数顺序分成8份，6位一份，B[8][6]。

7. 使用S[i]替换B[i][6]。过程如下: 取出B[i][6]的第1位和第6位连成一个2位数m， m就是S[i]中对应的行数(0-3)，取出B[i][6]的第2到第5位连成一个4位数n(0-15)，n就是S[i]中对应的列数，用S[i][m][n]代替B[i][6]。S是4行16列的对应表，里面是4位的数，一共有8个S，定义如下:

S[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[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[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[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[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[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[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[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,

8. 将从B[i][6]经过S得到的8个4位数连起来得到32位数。对这个数进行如下变换:

   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,

  得到的结果与L[i][32]作异或运算，把结果赋给R[i][32]。

9. 把R[i-1][32]的值赋给L[i]，从5开始循环。直到K[16][48]结束。

10. 将最后的L,R合并成64位，然后进行如下转化得到最后的结果。这是对第4步的一个逆变化。
 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

以上是Des的加密过程，解密过程同样，只需要把16个子密钥K[i][48]的顺序颠倒过来就行了。

代码:

/* filename: gy_des.cpp *//* *Some of codes are copyed from des.lib which is written by Eric Young ([e-mail]) *  You can get the lib from ftp://ftp.psy.uq.oz.au/pub/Crypto/DES/, */#include "stdafx.h"#include < bitset >#include < vector >#include < string >#include < iostream >using namespace std;//using namespace gy;typedef bitset< 4 > _b4;typedef bitset< 6 > _b6;typedef bitset< 8 > _b8;typedef bitset< 28 > _b28;typedef bitset< 32 > _b32;typedef bitset< 48 > _b48;typedef bitset< 56 > _b56;typedef bitset< 64 > _b64;typedef vector< _b8 > _vb8;typedef vector< _b48 > _vb48;typedef vector< _b64 > _vb64;namespace {const unsigned char odd_parity[256]={1,  1,  2,  2,  4,  4,  7,  7,  8,  8, 11, 11, 13, 13, 14, 14,16, 16, 19, 19, 21, 21, 22, 22, 25, 25, 26, 26, 28, 28, 31, 31,32, 32, 35, 35, 37, 37, 38, 38, 41, 41, 42, 42, 44, 44, 47, 47,49, 49, 50, 50, 52, 52, 55, 55, 56, 56, 59, 59, 61, 61, 62, 62,64, 64, 67, 67, 69, 69, 70, 70, 73, 73, 74, 74, 76, 76, 79, 79,81, 81, 82, 82, 84, 84, 87, 87, 88, 88, 91, 91, 93, 93, 94, 94,97, 97, 98, 98,100,100,103,103,104,104,107,107,109,109,110,110,112,112,115,115,117,117,118,118,121,121,122,122,124,124,127,127,128,128,131,131,133,133,134,134,137,137,138,138,140,140,143,143,145,145,146,146,148,148,151,151,152,152,155,155,157,157,158,158,161,161,162,162,164,164,167,167,168,168,171,171,173,173,174,174,176,176,179,179,181,181,182,182,185,185,186,186,188,188,191,191,193,193,194,194,196,196,199,199,200,200,203,203,205,205,206,206,208,208,211,211,213,213,214,214,217,217,218,218,220,220,223,223,224,224,227,227,229,229,230,230,233,233,234,234,236,236,239,239,241,241,242,242,244,244,247,247,248,248,251,251,253,253,254,254};const int keyperm_table56[56] = {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};const int keycompperm_table[48] = {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};const int keyshift_table[16] = {1, 1, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 1};const int datainitperm_table[64] = {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};const int dataexpperm_table[48] = {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};const int datasbox_table[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},}};const int datapperm_table[32] = {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};const int datafp_table[64] = {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};template < size_t _NB >void rotateleft_bitset(bitset< _NB >& input, size_t step){bitset< _NB > tmp = input;input <<= step;tmp >>= _NB - step;input |= tmp;}template < size_t _NB >void rotateright_bitset(bitset< _NB >& input, size_t step){bitset< _NB > tmp = input;input >>= step;tmp <<= _NB - step;input |= tmp;}template < class Input, class Output, class Table>void Des_Permutation( const Input& input, Output& output, const Table& table, size_t TableSize){for (size_t i = 0; i < TableSize; ++i) {output[i] = input[ table[i]-1 ];}}void Des_Key_Permutation1(const _b64& input, _b56& output){Des_Permutation(input, output, keyperm_table56, sizeof(keyperm_table56)/sizeof(int));}void Des_Key_CompPerm(const _b56& input, _b48& output){Des_Permutation(input, output, keycompperm_table, sizeof(keycompperm_table)/sizeof(int));}void Des_Key_Shift(_b56& key56, size_t step){_b28 l28, r28;int i;for (i = 0; i < 28; ++i) {r28[i] = key56[i];l28[i] = key56[28+i];}rotateleft_bitset(l28, step);rotateleft_bitset(r28, step);for (i = 0; i < 28; ++i) {key56[i] = r28[i];key56[28+i] = l28[i];}}void Des_Key_Generate(const _b64& key, _vb48& subkey){_b56 tmp56;Des_Key_Permutation1(key, tmp56);for (int i = 0; i < 16; ++i) {_b48 tmp48;Des_Key_Shift(tmp56, keyshift_table[i]);Des_Key_CompPerm(tmp56, tmp48);cout << "Key: " << tmp48 << endl;subkey.push_back(tmp48);}}void Des_Char_To_Binary(char c, string& binary){unsigned char tmp = odd_parity[c];binary.append( (tmp & 0x80) ? "1" : "0"  );binary.append( (tmp & 0x40) ? "1" : "0"  );binary.append( (tmp & 0x20) ? "1" : "0"  );binary.append( (tmp & 0x10) ? "1" : "0"  );binary.append( (tmp & 0x08) ? "1" : "0"  );binary.append( (tmp & 0x04) ? "1" : "0"  );binary.append( (tmp & 0x02) ? "1" : "0"  );binary.append( (tmp & 0x01) ? "1" : "0"  );}void Des_String_To_Binary(const string& input, _b64& output){string binary;for (int i = 0; i < input.length(); ++i ) {Des_Char_To_Binary(input[i], binary);}_b64 tmp64(binary);output = tmp64;}void Des_String_To_Key(const string& key, _vb48& subkey){_b64 tmp64;Des_String_To_Binary(key, tmp64);Des_Key_Generate(tmp64, subkey);}void Des_Data_ExpPerm(const _b32& input, _b48& output){Des_Permutation(input, output, dataexpperm_table, sizeof(dataexpperm_table)/sizeof(int));}void Des_Data_IP(const _b64& input, _b64& output){Des_Permutation(input, output, datainitperm_table, sizeof(datainitperm_table)/sizeof(int));}void Des_Data_S(const _b6& input, _b4& output, int step){bitset< 2 > tmp2;_b4 tmp4;tmp2[0] = input[5];tmp2[1] = input[0];tmp4[0] = input[1];tmp4[1] = input[2];tmp4[2] = input[3];tmp4[3] = input[4];_b8 t8(datasbox_table[step][tmp2.to_ulong()][tmp4.to_ulong()]);for (int i = 0; i < 4; ++i) {output[i] = t8[i];}}void Des_Data_S(const _b48& input, _b32& output){_b6 tmp6;_b4 tmp4;int i, j;for (i = 0; i < 8; ++i) {for (j = 6; j < 0; --j) {tmp6[j] = input[ 47 - i*6 - j];}Des_Data_S(tmp6, tmp4, i);for (j = 0; j < 4; ++j) {output[ 31 - (i << 2) - j] = tmp4[j];}}}void Des_Data_P(const _b32& input, _b32& output){Des_Permutation(input, output, datapperm_table, sizeof(datapperm_table)/sizeof(int));}void Des_Data_F(_b64& input, const _b48& key){_b32 l32, r32, tmp32, t32;_b48 exp48;int i;for (i = 0; i < 32; ++i ) {r32[i] = input[i];l32[i] = input[32+i];}//cout << "r32** " << r32 << endl;Des_Data_ExpPerm(r32, exp48);//cout << "exp** " << exp48 << endl;//cout << "key** " << key << endl;exp48 ^= key;//cout << "exp** " << exp48 << endl;Des_Data_S(exp48, tmp32);//cout << "tmp** " << tmp32 << endl;Des_Data_P(tmp32, t32);//cout << "t32** " << t32 << endl;t32 ^= l32;l32 = r32;r32 = t32;for (i = 0; i < 32; ++i ) {input[i] = r32[i];input[32+i] = l32[i];}}void Des_data_FP(const _b64& input, _b64& output){Des_Permutation(input, output, datafp_table, sizeof(datafp_table)/sizeof(int));}int Des_encode_64bit(const _vb48& key, const _b64 &data, _b64 &output){_b64 tmp64;Des_Data_IP(data, tmp64);for (int i = 0; i < 16; ++i) {//cout << "" << tmp64 << endl;Des_Data_F(tmp64, key[i]);//cout << "" << tmp64 << endl;}Des_data_FP(tmp64, output);return 0;}int Des_encode(const string& key, const string& data, _b64 &output){_vb48 subkey, decodekey;_b64 data64, tmp64;Des_String_To_Key(key, subkey);for (int i = 0; i < 16; ++i) {decodekey.push_back(subkey[ 15-i ]);}Des_String_To_Binary(data, data64);//cout << "data:" << data64 << endl;Des_encode_64bit(subkey, data64, output);//cout << "code:" << output << endl;Des_encode_64bit(decodekey, output, tmp64);//cout << "reco:" << tmp64 << endl;if (tmp64 == data64) {cout << "Congratulation.$$$$$$$$$$$___FCKpd___1quot; << endl;}else {cout << "Error. **************************" << endl;}return 0;}int Des_decode(const string& key, const string& data, _b64 &output){return 0;}}namespace gy {/* Mode: true for encode, false for decode */int Des(const string& key, const string& data, _b64 &output, bool Mode){if (Mode) {return Des_encode(key, data, output);}else {return Des_decode(key, data, output);}}void Run_Des(void) {int select = 0;string data, key;cout << "1. encode;" << endl << "2. decode;" << endl << "Your choise: ";cin >> select;cout << endl << "Please input the data: ";cin >> data;cout << endl << "Please input the key: ";cin >> key;_b64 output;if (select == 1) {Des(key, data, output, true);}else {Des(key, data, output, false);}}}原文：http://bbs.sdu.edu.cn/pc/pccon.php?id=675&nid=28248&order=c&tid=