DES原理浅析

最新推荐文章于 2022-12-11 10:02:21 发布

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最新推荐文章于 2022-12-11 10:02:21 发布

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CC 4.0 BY-SA版权

分类专栏：加密解密

本文链接：https://blog.youkuaiyun.com/xboxmicro/article/details/23135017

本文介绍了DES加密原理，包括其明文和密钥长度，加密流程，IP置换，L和R的划分，F_func函数，S-Box非线性代换，以及密钥生成过程。通过代码解析，详细阐述了DES的16轮加密过程及解密步骤。

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在学习密码学过程中，我将DES的一个简单的代码发上来（学习中~），并通过代码解释DES加密的原理

首先先上一个头文件

DES.h

//初始置换表IP
int IP_Table[64] = 
{   
	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,
	56,48,40,32,24,16,8,0,
	58,50,42,34,26,18,10,2,
	60,52,44,36,28,20,12,4,
	62,54,46,38,30,22,14,6
}; 

//逆置换表IP-1
int IP_1_Table[64] = 
{   
	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,
	32,0,40,8,48,16,56,24
};

//密钥置换选择1
int PC_1[56] = 
{   
	56,48,40,32,24,16,8,
	0,57,49,41,33,25,17,
	9,1,58,50,42,34,26,
	18,10,2,59,51,43,35,
	62,54,46,38,30,22,14,
	6,61,53,45,37,29,21,
	13,5,60,52,44,36,28,
	20,12,4,27,19,11,3
};

//密钥置换选择2
int PC_2[48] = 
{   
	13,16,10,23,0,4,2,27,
	14,5,20,9,22,18,11,3,
	25,7,15,6,26,19,12,1,
	40,51,30,36,46,54,29,39,
	50,44,32,46,43,48,38,55,
	33,52,45,41,49,35,28,31
};

int LOOP_Table[16] = {1,1,2,2,2,2,2,2,1,2,2,2,2,2,2,1};   

//扩充置换表E
int E_Table[48] = 
{ 
	31, 0, 1, 2, 3, 4,
	3,  4, 5, 6, 7, 8,
	7,  8,9,10,11,12,
	11,12,13,14,15,16,
	15,16,17,18,19,20,
	19,20,21,22,23,24,
	23,24,25,26,27,28,
	27,28,29,30,31, 0
};

//置换函数P P-盒
int P_Table[32] = 
{
	15,6,19,20,28,11,27,16,
	0,14,22,25,4,17,30,9,
	1,7,23,13,31,26,2,8,
	18,12,29,5,21,10,3,24
};

//S盒
char S_Box[8][4][16] =//S1
{
  
  {
  
  {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}},
//S2
{
  
  {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}},
//S3
{
  
  {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}},
//S4
{
  
  {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}},
//S5
{
  
  {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}},
//S6
{
  
  {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}},
//S7
{
  
  {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}},
//S8
{
  
  {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}}};

bool SubKey[16][48];

void SetSubKey(const char Key[8]);
void ByteToBit(bool *Out, const char *In, int bits);
void BitToByte(char *Out, const bool *In, int bits);
void TransForm(bool *Out, bool *In, int *Tab