des16.cpp

由于BT老师的要求

// DES16.cpp: implementation of the CDES16 class.
//
//////////////////////////////////////////////////////////////////////

#include "stdafx.h"
#include "DES16.h"

void DES(unsigned char *bufferin,unsigned char *bufferout, unsigned char *key,long mode)
{
//密钥变换为14字节(去掉校验位)
static unsigned char pc1[14]={13,5,1,11,8,3,9,10,4,0,12,6,14,2};

//14字节变换为12字节(数据压缩)
static unsigned char pc2[12]={6,0,12,2,11,8,4,10,7,1,13,5};

//8字节变换为12字节(数据扩展)
static unsigned char exp[12] = {7,0,1,2,3,4,3,4,5,6,7,0};

//64位数据IP(Initial Permutation)变换表
static unsigned char ip[16] = {
13, 9, 5, 1,
15,11, 7, 3,
12, 8, 4, 0,
14,10, 6, 2 };

//数据逆置换(Final Permutation)
static unsigned char ip_1[16] = {
11, 3,15, 7,
10, 2,14, 6,
 9, 1,13, 5,
 8, 0,12, 4 };

//Permutation P
static unsigned char pp[8] = {7,6,0,4,1,2,5,3};

/* INITIALIZE THE TABLES */
/* Table - s1 */
static unsigned char s1[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 };

/* Table - s2 */
static unsigned char s2[4][16] = {
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 };

 
/* 密钥生成中的循环左移位的累计次数*/
static unsigned char totrot[] = {1, 2, 4, 6};


long i, j, k; 
long rotshift;                              //密钥移位次数 
unsigned char keybuf[17];                   //密钥，密钥16字节缓冲区
unsigned char keyreal[15], keys[5][13];    //实际使用14字节密钥,12字节密钥数组 
unsigned char srcbuf[17], dstbuf[17];       //明文，密文16字节缓冲区
unsigned char L[5][9], R[5][9], LR[17], RL[17];    //加密时临时数据左右两部分
unsigned char E[5][13];                    //R数组的扩展数据
unsigned char B[3][7], BB[9], P[9];       //E和K异或后的缓冲数组
unsigned char C[5][8], D[5][8], CD[15]; //56字节密钥的左右两部分
unsigned char temp1, temp2, m, n, x;	//存放临时数据

 
//1.变换密钥
//密钥不足2字节则用0补足(或自定义)
//将2字节密钥转换为16字节字串 

for(i=0;i<2;i++)
{
	j = *(key+i);
	keybuf[8*i] = (j / 128) % 2;
	keybuf[8*i+1] = (j / 64) % 2;
	keybuf[8*i+2] = (j / 32) % 2;
	keybuf[8*i+3] = (j / 16) % 2;
	keybuf[8*i+4] = (j / 8) % 2;
	keybuf[8*i+5] = (j / 4) % 2;
	keybuf[8*i+6] = (j / 2) % 2;
	keybuf[8*i+7] = (j / 1) % 2;
}

 
//根据pc1进行变换成14字节，去掉奇偶校验位
for(i=0;i<14;i++)
{
	keyreal[i] = keybuf[pc1[i]];
}


//将14字节密钥分为左右两部分C[0],D[0]

for(i=0;i<7;i++)
{
	C[0][i] = keyreal[i];
	D[0][i] = keyreal[i+7];
} 

 

//循环4次(i从1开始)
for(i=1;i<5;i++)
{
	//根据加密或解密确定密钥顺序
	if(mode)    //加密
		rotshift = totrot[i-1];
	else        //解密
		rotshift = totrot[4-i];

 
	//1)左移固定位数得到C[i]和D[i];
	for(j=0;j<7;j++)
	{
		C[i][j] = C[0][j];
		D[i][j] = D[0][j];
	}

	for(j=0;j<rotshift;j++)
	{
		temp1 = C[i][0];
		temp2 = D[i][0];
		for(k=0;k<7;k++)
		{
			C[i][k] = C[i][k+1];
			D[i][k] = D[i][k+1];
		}
		C[i][6] = temp1;
		D[i][6] = temp2;
	} 

	//2)将C[i]D[i]用pc2化简为12位k[i];
	for(j=0;j<7;j++)
	{
		CD[j] = C[i][j];
		CD[j+7] = D[i][j];
	}

	for(j=0;j<12;j++)
	{
		keys[i][j] = CD[pc2[j]];
	}
}

 
//2.数据处理
//若明文不足2字节则补0(或自定义)
//将2字节数据转换为16字节字串

for(i=0;i<2;i++)
{
	j = *(bufferin+i);
	srcbuf[i*8] = (j / 128) % 2;
	srcbuf[i*8+1] = (j / 64) % 2;
	srcbuf[i*8+2] = (j / 32) % 2;
	srcbuf[i*8+3] = (j / 16) % 2;
	srcbuf[i*8+4] = (j / 8) % 2;
	srcbuf[i*8+5] = (j / 4) % 2;
	srcbuf[i*8+6] = (j / 2) % 2;
	srcbuf[i*8+7] = (j / 1) % 2;
}

//将srcbuf按ip进行变换
for(i=0;i<16;i++) LR[i] = srcbuf[ip[i]];

//将16字节数据转换为两部分L[0],R[0]
for(i=0;i<8;i++)
{
	L[0][i] = LR[i];
	R[0][i] = LR[i+8];
}

//循环4次(i从1开始)，用密钥加密数据
for(i=1;i<5;i++)
{
	//1)将8位的R[i-1]按exp扩展为12位的E[i-1];
	for(j=0;j<12;j++)
	{
		E[i-1][j] = R[i-1][exp[j]];
	}

	//2)异或E[i-1]和K[i];
	for(j=0;j<12;j++)
	{
		keys[i][j] = keys[i][j] ^ E[i-1][j];
	}

	//3)将异或结果分为2个6位长的部分B[8]

	for(j=0;j<2;j++)
	{
		B[j][0] = keys[i][j*6];
		B[j][1] = keys[i][j*6+1];
		B[j][2] = keys[i][j*6+2];
		B[j][3] = keys[i][j*6+3];
		B[j][4] = keys[i][j*6+4];
		B[j][5] = keys[i][j*6+5];
	}

	//4)循环用S表替换(j从1开始)
	for(j=0;j<2;j++)
	{
		//a)B[j]第1位和第6位组合为M，作为S[j]的行号
		m = 2 * B[j][0] + B[j][5]; 

		//b)B[j]第2到5位组合为N，作为S[j]的列号
		n = 2 * (2 * (2 * B[j][1] + B[j][2]) + B[j][3]) + B[j][4];

		//c)用S[j][M][N]来取代B[j]
		switch(j)
		{
			case 0:
				x = s1[m][n];
				break;

			case 1:
				x = s2[m][n];
				break;
		}
		BB[j*4] = (x / 8) % 2;
		BB[j*4 + 1] = (x / 4) % 2;
		BB[j*4 + 2] = (x / 2) % 2;
		BB[j*4 + 3] = (x / 1) % 2;
	}


	//5)将B[1]到B[8]按P组合得到p
	for(j=0;j<8;j++)
	{
		P[j] = BB[pp[j]];
	}

	//6)R[i] = p xor L[i-1];L[i] = R[i-1];
	for(j=0;j<8;j++)
	{
		R[i][j] = P[j] ^ L[i-1][j]; 
		L[i][j] = R[i-1][j];
	} 
}

//3.组合变换后的R[4]L[4]按ip_1变换得到最后结果

for(i=0;i<8;i++)
{
	RL[i] = R[4][i];
	RL[i+8] = L[4][i];
}

for(i=0;i<16;i++)
{
	dstbuf[i] = RL[ip_1[i]];
}

//将16字节数据转换为2字节
for (i=0;i<2;i++) 
{
	*(bufferout + i) = dstbuf[8*i]*128 + dstbuf[8*i+1]*64 + dstbuf[8*i+2]*32 + dstbuf[8*i+3]*16 + dstbuf[8*i+4]*8 + dstbuf[8*i+5]*4 + dstbuf[8*i+6]*2 + dstbuf[8*i+7] ;
}
return;
}