des解密python des解密在线

// DES算法利用一个56+8奇偶校验位(第8,16,24,32,40,48,56,64位)=64位的密钥对以64位为单位的块数据进行加解密
#include "memory.h"
#include "stdio.h"
#include "conio.h"

enum    { ENCRYPT, DECRYPT };// ENCRYPT:加密,DECRYPT:解密
void Des_Run(char Out[8], char In[8], char Type);
void Des_SetKey(const char Key[8]);// 设置密钥
static void F_func(char In[32], const char Ki[48]);// f 函数
static void S_func(char Out[32], const char In[48]);// S 盒代替
static void Transform(char *Out, char *In, const char *Table, int len);// 变换
static void Xor(char *InA, const char *InB, int len);// 异或
static void RotateL(char *In, int len, int loop);// 循环左移
static void ByteToBit(char *Out, const char *In, int bits);// 字节组转换成位组
static void BitToByte(char *Out, const char *In, int bits);// 位组转换成字节组

/*
* 子密钥生成：
* 1. 密钥先被转化成64比特的二进制；
* 2. 再按照密钥置换函数PC-1(8x7)进行压缩置换，变成56位；
* 3. 将其置换的输出再分为前28位C0和后28位D0两部分；
* 4. 进行16轮数据处理，每一轮中，先将C0和D0 分别 进行循环左移，
* 	 再将两部分左移结果 一起执行压缩置换PC-2(8X6)，最后生成16个48位的子密钥。
*/
//PC1选位表(子密钥生成置换表1) 把密钥中的奇偶校验为去掉（不包含8,16,24,32,40,48,56,64），变成56位；
const static char PC1_Table[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
};
//PC2选位表(子密钥生成置换表2) 生成子密钥 48位
const static char PC2_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
};

//左移位数表 
const static char LOOP_Table[16] = {
	1, 1, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 1
};

/*
* 加密：DES算法是对固定大小(64位)的数据块进行加密解密操作的；
* 明文串M经过长度都为48位的16个子密钥K来加密，最后生成长度为64比特的密文E；经过长度都为48位的16个子密钥K来加密，最后生成长度为64比特的密文E；
* 1. 进行IP初始置换，将该明文串M(64bit)被分为32位的左半部分L0和32位的右半部分R0两部分；
* 2. 将数据的右半部分R0通过扩展置换E从32位扩展为48位；
* 3. 扩展后的48位与K1进行异或；
* 4. 异或后的结果通过S盒子转换为32位；
* 5. 输出结果再通过一个P盒置换产生一个32位的输出；
* 6. 最后，P盒置换的结果与左半部分进行异或运算，然后将左右两部分交换，之后进入下一轮迭代。
* 7. 在完成完全相同的16轮运算后，将得到的两部分数据L16和R16合在一起，即L16R16；(L16:指进行了16轮处理得到的32位左半部分数据)
* 8. 将L16与R16的位置交换,得到R16L16，再经过一个末置换函数IP-1，即可得到64位的密文。
*
*/
//置换IP表
const static char IP_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
};
//逆置换IP-1表
const static char IPR_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
};
//E位选择表(扩展置换表)
static const char E_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
};
//P换位表(单纯换位表)
const static char P_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
};

// S盒
const static 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
};

static char SubKey[16][48];// 16圈子密钥

void Des_Run(char Out[8], char In[8], char Type)
{
	static char M[64], Tmp[32], *Li = &M[0], *Ri = &M[32];
	ByteToBit(M, In, 64);// 字节组转换成位组
	Transform(M, M, IP_Table, 64);// 变换
	if (Type == ENCRYPT){
		for (int i = 0; i<16; i++) {
			memcpy(Tmp, Ri, 32);
			F_func(Ri, SubKey[i]);
			Xor(Ri, Li, 32);// 异或
			memcpy(Li, Tmp, 32);
		}
	}
	else{
		for (int i = 15; i >= 0; i--) {
			memcpy(Tmp, Li, 32);
			F_func(Li, SubKey[i]);
			Xor(Li, Ri, 32);// 异或
			memcpy(Ri, Tmp, 32);
		}
	}
	Transform(M, M, IPR_Table, 64);// 变换
	BitToByte(Out, M, 64);
}


void Des_SetKey(const char Key[8])
{
	static char K[64], *KL = &K[0], *KR = &K[28];
	ByteToBit(K, Key, 64);// 字节组转换成位组
	Transform(K, K, PC1_Table, 56);// 变换
	for (int i = 0; i<16; i++)
	{
		RotateL(KL, 28, LOOP_Table[i]);// 循环左移
		RotateL(KR, 28, LOOP_Table[i]);// 循环左移
		Transform(SubKey[i], K, PC2_Table, 48);// 变换
	}
}



void F_func(char In[32], const char Ki[48])// f 函数
{
	static char MR[48];
	Transform(MR, In, E_Table, 48);// 变换
	Xor(MR, Ki, 48);// 异或
	S_func(In, MR);// S 盒代替
	Transform(In, In, P_Table, 32);// 变换
}

void S_func(char Out[32], const char In[48])// S 盒代替,输入6位的数，输出4位的数，将第一六位对应的十进制数作为行，第二三四五为的对应十进制数作为列
{
	for (char i = 0, j, k; i<8; i++, In += 6, Out += 4) // 输出数据存放位置out下标不断增进
	{
		j = (In[0] << 1) + In[5];
		k = (In[1] << 3) + (In[2] << 2) + (In[3] << 1) + In[4];
		ByteToBit(Out, &S_Box[i][j][k], 4); // out每次都会前进4个位置（char）
	}
}

void Transform(char *Out, char *In, const char *Table, int len)//变换
{
	static char Tmp[256];
	for (int i = 0; i < len; i++)
	{
		Tmp[i] = In[Table[i] - 1];
	}
	memcpy(Out, Tmp, len);
}



void Xor(char *InA, const char *InB, int len)//异或
{
	for (int i = 0; i < len; i++)
	{
		InA[i] ^= InB[i];
	}
}

void RotateL(char *In, int len, int loop)//循环左移
{
	static char Tmp[256];
	memcpy(Tmp, In, loop);
	memcpy(In, In + loop, len - loop);
	memcpy(In + len - loop, Tmp, loop);
}

void ByteToBit(char *Out, const char *In, int bits)//字节组转换成位组
{
	for (int i = 0; i < bits; i++)
	{
		Out[i] = (In[i / 8] >> (i % 8)) & 1;
	}
}

void BitToByte(char *Out, const char *In, int bits)
{
	memset(Out, 0, (bits + 7) / 8);
	for (int i = 0; i < bits; i++)
	{
		Out[i / 8] |= In[i] << (i % 8);
	}
}


int main()
{
	char key[8] = { 1, 9, 8, 0, 9, 1, 7, 2 }, str[] = "Hello, world";
	puts("Before encrypting");
	puts(str);
	Des_SetKey(key);
	Des_Run(str, str, ENCRYPT);
	puts("After decrypting");
	puts(str);
	puts("After decrypting");
	Des_Run(str, str, DECRYPT);
	puts(str);

	return 0;
}

结果：