DES加密算法
参考【web安全|DES加密算法】本文将从基本原理，加密过程，子密钥生成过程对DES进行讲解。源码可在github中找到，文末也会贴出源码。
- 《密码编码与信息安全——C++实践》
- 参考“DES加密算法｜密码学｜信息安全” https://www.bilibili.com/video/BV1KQ4y127AT?from=search&seid=1358372623996612630&spm_id_from=333.337.0.0
https://github.com/yingmuzhi/cryptology/blob/main/DES.cpp
基本原理
- DES算法是属于对称密码算法中的分组加密算法。
分组加密属于块加密，对一个字节块进行加密。与分组加密对应的是流加密，流加密指一个字节一个字节加密。 - 密钥长64bit，56bit参与运算，其余8bit为校验位。分别取自{8, 16, 24, 32, 40, 48, 56, 64}位。
- 当n个64bit明文数据块都经过DES加密处理后，所得到的n个64bit密文数据块串在一起就是密文。
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- IP置换（Initial Permutations）
将原来的64bit二进制位重新排序
- 轮函数——E扩展置换
将32bit输入扩展为48bit输出
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- 48bit明文和48bit密钥异或后，再使用8个S盒压缩处理得到32bit数据，这是一个非线性运算
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- P盒置换，32bit->32bit。再和L0异或
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- IPI置换
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- 使用PC1置换算法，64bit->56bit
- 分组循环左移（若求解密密钥则是分组循环右移）
- 合并后使用PC2置换算法，56bit->48bit
/*
* @Descripttion: refer to "密码编码与信息安全:C++实践"
* @version:
* @Author: MuzhiYing
* @Date: 2022-03-23 14:36:55
* @LastEditors: MuzhiYing
* @LastEditTime: 2022-03-23 16:40:16
*/#include
#include
#include
using std::vector;
using namespace std;
// using namespace std::cout;
// using namespace std::endl;
// using namespace std::string;
// unsigned int 刚好是 64bit = 8Byte = 8 * char
class DES
{
public:
DES();
// 构造函数
// function
void setKey(string k);
// 设置初始密钥的函数
void setPlainText(string p);
// 设置明文的函数
unsigned long long permutations(unsigned long long num, const int p[], int pmax, int n);
// 用于密钥生成、加解密过程的各类置换的函数
void genEncKey();
// 生成加密、解密的子密钥的过程
unsigned long long SBoxes(unsigned long long num);
// S盒计算
void encryption();
// 用于加密函数
void decryption();
// 用于解密函数
void showBinary(unsigned long long num);
// 将数据以二进制形式显示的函数，用于检查数据计算过程
void showResult();
// 用于显示解密，解密结果的函数
private:
unsigned long long keyShift(unsigned long long k, int n);
unsigned long long key;
// 输入的密钥
unsigned long long plainText;
// 明文
unsigned long long cipherText;
// 密文
unsigned long long decipherText;
// 经过解密后的密文，理论上应该等于明文
unsigned long long encKey[16];
// 由密钥生成的16个子密钥
static const int IP[64];
// 初始IP置换
static const int IPI[64];
// IP置换的逆置换
static const int keyIP[56];
// 密钥置换数组，将密钥从64bit->56bit
static const int encKeyRound[16];
// 生成子密钥时左移数组
static const int CP[48];
// 密钥压缩置换数组，将密钥从56bit->48bit
static const int EP[48];
// 扩展置换的数组，将明文从32bit->48bit
static const int SBox[32][16];
// S盒运算
static const int P[32];
// S盒运算后的P置换数组
};
/// 初始化
DES::DES(){
key = 0;
plainText = 0;
cipherText = 0;
decipherText = 0;
}/// 用于加密。将进来的明文进行ip置换，64bit->64bit
const int DES::IP[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};
/// 用于加密。将经过16轮轮变换的text进行ipi置换，即ip逆置换，64bit->64bit
const int DES::IPI[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};
/// 用于生成密钥。将密钥PC1置换，64bit->56bit
const int DES::keyIP[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};
/// 用于生成密钥。生成子密钥时左移数组个数
const int DES::encKeyRound[16] = {1, 1, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 1};
/// 用于生成密钥。PC2置换，56bit->48bit
const int DES::CP[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};
/// 用于加密中轮运算。E扩展置换，32bit->48bit
const int DES::EP[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};
/// 用于加密中轮运算。S盒置换，48bit->32bit
const int DES::SBox[32][16] = {
14,4, 13,1,2, 15, 11,8,3, 10,6, 12,5,9,0,7, //S1
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, //S2
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, //S3
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, //S4
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, //S512,1, 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, //S64, 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,//S713,2,8,4,6, 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//S8
};
/// 用于加密中轮运算。P盒置换，32bit->32bit
const int DES::P[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};
/// 输入密钥为8Byte的字符串，转换为unsigned long long 类型 64bit
void DES::setKey(string k)
{
int i ;
unsigned long long c;
for (i = 0;
i< 8;
i++){
c = k[i];
key = (c<<(7-i) * 8) | key;
// key等于左移后的c
}
}
/// 输入明文为8Byte的字符串，转换为unsigned long long 类型 64bit
void DES::setPlainText(string p){
int i;
unsigned long long c;
for (i = 0;
i< 8;
i++){
c = p[i];
plainText = (c<<(7-i)*8) | plainText;
}
}
/// 生成子密钥
void DES::genEncKey(){
unsigned long long gkey;
gkey = permutations(key, keyIP, 64, 56);
// 密钥初始置换。64bit->56bit
int i;
for(i=0;
i<16;
i++){
gkey = keyShift(gkey, encKeyRound[i]);
// 左移
encKey[i] = permutations(gkey, CP, 56, 48);
// 密钥压缩置换。56bit->48bit
}
}
/// 密钥循环左右移
unsigned long long DES::keyShift(unsigned long long k, int n){
unsigned long long tempKey = 0;
unsigned long long L, R;
L = (k&0xFFFFFFF0000000LL)>>28;
//cout<<"L:"<>27)&1);
R = ((R&0x7FFFFFF)<<1) | ((R>>27)&1);
tempKey = (L<<28) | R;
}else if(n==2){
L = ((L&0x3FFFFFF)<<2) | ((L>>26)&3);
R = ((R&0x7FFFFFF)<<2) | ((R>>26)&3);
tempKey = (L<<28) | R;
}
return tempKey;
}
/// 根据数组要求，实现置换
unsigned long long DES::permutations(unsigned long long num, const int p[], int pmax, int n){
unsigned long long temp = 0;
int i;
for(i=0;
i> (pmax - p[i])) & 1;
}
return temp;
}
/// S盒运算
unsigned long long DES::SBoxes(unsigned long long num){
int i;
unsigned long long temp;
unsigned long long result = 0;
for (i=0;
i<8;
++i){
temp = (num >> ((7-i) * 6)) & 0x3F;
int x = ((temp>>4) & 0x2) | (temp & 0x1) + i*4;
int y = (temp>>1) & 0xF;
temp = SBox[x][y];
temp = temp << ((7-i)*4);
result |= temp;
}
return result;
}
/// 加密总过程
void DES::encryption(){
unsigned long long temp = permutations(plainText, IP, 64, 64);
int i;
unsigned long long L, R, tempR;
L = (temp & 0xFFFFFFFF00000000LL) >> 32;
R = (temp & 0x00000000FFFFFFFFLL);
tempR = R;
for(i = 0;
i<16;
i++){
tempR = permutations(R, EP, 32, 48);
tempR = tempR ^ encKey[i];
tempR = SBoxes(tempR);
tempR = permutations(tempR, P, 32, 32);
tempR ^= L;
L = R;
R = tempR;
cout<<"L["<> 32;
R = (temp & 0x00000000FFFFFFFFLL);
tempR = R;
for(i = 0;
i<16;
i++){
tempR = permutations(R, EP, 32, 48);
tempR = tempR ^ encKey[15-i];
// 密钥生成方顺序不同
tempR = SBoxes(tempR);
tempR = permutations(tempR, P, 32, 32);
tempR ^= L;
L = R;
R = tempR;
}
temp = (R<<32) | L;
temp = permutations(temp, IPI, 64, 64);
decipherText = temp;
}
/// 二进制结果展示
void DES::showBinary(unsigned long long num){
std::vector v;
do{
v.push_back(num % 2);
num = (num - num%2) / 2;
}while(num != 0);
for(int i=(v.size()-1);
i>=0;
i--){
cout<
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