DES加密解密算法實現

DES加密解密

數據加密標準(Data Encryption Standard, DES)中的算法是第一個也是最重要的現代對稱加密算法，其分組長度爲64比特，使用的密鑰長度爲56比特(實際上函數要求一個64位的密鑰作爲輸入，但其中用到的有效長度只有56位，剩餘8位可作爲奇偶校驗位或完全隨意設置)，DES加解密過程類似，加解密使用同樣的算法，唯一不同的是解密時子密鑰的使用次序要反過來。DES的整個體制是公開的，系統安全性完全依靠密鑰的保密。

加密流程

運行模式

常見的四種模式如下：

模式	描述	用途
電碼本模式(ECB)	每個明文組獨立地以同一密鑰加密	傳送短數據(如一個加密密鑰)
密碼分組鏈接模式(CBC)	加密算法的輸入是當前明文組與前一密文組的異或	傳送數據分組；認證
密碼反饋模式(CFB)	每次只處理輸入的j比特，將上一次的密文作加密算法的輸入以產生僞隨機輸出，該輸出再與當前明文異或以產生當前密文	傳送數據流；認證
輸出反饋模式(OFB)	與CFB類似不同之處是本次加密算法的輸入爲前一次加密算法的輸出	有繞信道上(如衛星通信)傳送數據流

c++代碼實現DES加密解密

#include<iostream>
#include<math.h>
using namespace std;

//IP置換表
int 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
};

//IP-1逆置換表
int IP_1[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擴展置換表
int E[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置換表，引起雪崩效應
int 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
};

//PC-1置換表
int PC_1[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
};

//PC-2置換表
int PC_2[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
};

//左移位數表 
int LeftMove[16] = {
    1,1,2,2,2,2,2,2,1,2,2,2,2,2,2,1
};

// 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 bool SubKey[16][48];//用於存儲16輪子密鑰

void ByteToBit(bool *Out, const char *In, int bits)//字節轉換成8位二進制
{
    for(int i = 0; i < bits; i++)
    {
        Out[i] = (In[i/8] >> (i%8)) & 1;
    }
}

void BitToByte(char *Out, const bool *In, int bits)//8位二進制轉換成字節
{
    memset(Out, 0, (bits+7)/8);
    for(int i = 0; i < bits; i++)
    {
        Out[i/8] |= In[i] << (i%8);
    }
}

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

void RotateL(bool *In, int len, int loop)//循環左移
{
    static bool Tmp[256];
    memcpy(Tmp, In, loop);
    memcpy(In, In+loop, len-loop);
    memcpy(In+len-loop, Tmp, loop);
}

void Transform(bool *Out, bool *In, int *Table, int len)//對應置換表進行置換的函數
{
    static bool Tmp[256];
    for(int i = 0; i < len; i++)
    {
        Tmp[i] = In[ Table[i] - 1 ];
    }
    memcpy(Out, Tmp, len);
}

void Des_SetKey(const char Key[8])
{
    static bool K[64], *KL = &K[0], *KR = &K[28];
    ByteToBit(K, Key, 64);                      //字節轉換成8位二進制
    Transform(K, K, PC_1, 56);				    //PC-1變換
    for(int i=0; i<16; i++) 
    {
        RotateL(KL, 28, LeftMove[i]);           //循環左移
        RotateL(KR, 28, LeftMove[i]);           //循環左移
        Transform(SubKey[i], K, PC_2, 48);      //PC-2變換
    }
}

//S盒,輸入6位的數，輸出4位的數，將1,6位對應的十進制數作爲行，2,3,4,5位對應的十進制數作爲列
void S_func(bool Out[32], const bool In[48])
{
    for(char i=0,j,k; i<8; i++,In+=6,Out+=4) 
    {
        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);
    }
}

void F_func(bool In[32], const bool Ki[48])// f 函數
{
    static bool MR[48];
    Transform(MR, In, E, 48);//E擴展置換
    Xor(MR, Ki, 48);
    S_func(In, MR);
    Transform(In, In, P, 32);//P置換
}

void Des_Run(char Out[8], char In[8], bool Type) //加密解密主函數
{
    static bool M[64], Tmp[32], *Li = &M[0], *Ri = &M[32];
    ByteToBit(M, In, 64);               //字節轉換成8位二進制
    Transform(M, M, IP, 64);            //IP置換
    if(Type == 0)			  //加密算法
	{
		for(int i=0; i<16; i++)
		{
			memcpy(Tmp, Ri, 32);
			F_func(Ri, SubKey[i]);
			Xor(Ri, Li, 32);
			memcpy(Li, Tmp, 32);
        }
    }else if(Type == 1)     //解密算法
	{
        for(int i=15; i>=0; i--)
		{
            memcpy(Tmp, Li, 32);
            F_func(Li, SubKey[i]);
            Xor(Li, Ri, 32);
            memcpy(Ri, Tmp, 32);
        }
    }
    Transform(M, M, IP_1, 64);      //IP-1逆置換
    BitToByte(Out, M, 64);         //8位二進制轉換成字節
}

int main()
{
	int len,m,n,i,j;			
	char key[8],p[100],c[100];
	char str[8];
	cout<<"請輸入你要加密的密文："<<endl;
    gets(p);
	cout<<endl;
    cout<<"請輸入祕鑰（8位）："<<endl;
    gets(key);
	cout<<endl;

	//這裏計算明文長度用於8個字符分組
	len=strlen(p);
	m=floor(len/8);
	n=len%8;

	//不夠8位進行填充
	for(i=len;i<(m+1)*8;i++)
		p[i]='0';
    cout<<"加密前的明文："<<endl;
	for(i=0;i<len;i++)
		cout<<p[i];
	cout<<endl;
	cout<<endl;
	
	//加密
	Des_SetKey(key);
	for(i=0;i<m+1;i++)
	{
		for(j=0;j<8;j++)
			str[j]=p[i*8+j];
		Des_Run(str,str,0);
		for(j=0;j<8;j++)
			c[i*8+j]=str[j];
	}
	cout<<"加密後得到的密文："<<endl;
	for(i=0;i<(m+1)*8;i++)
		cout<<c[i];
	cout<<endl;
	cout<<endl;

	//反解密
   for(i=0;i<m+1;i++)
	{
		for(j=0;j<8;j++)
			str[j]=c[i*8+j];
		Des_Run(str,str,1);
		for(j=0;j<8;j++)
			p[i*8+j]=str[j];
	}
	cout<<"反解密後得到的明文："<<endl;
	for(i=0;i<len;i++)
		cout<<p[i];
	cout<<endl;
	cout<<endl;
	
    return 0;
	
}

ECB模式

將主程序改爲：

int main()
{
	char key[8];
    char *str=new char[8];
    cout<<"請輸入祕鑰（8位）："<<endl;
    gets(key);
    cout<<"請輸入你要加密的密文（8位）："<<endl;
    gets(str);
    cout<<"加密前的明文："<<endl;
    puts(str);
    Des_SetKey(key);
    Des_Run(str,str,0);

    cout<<"加密後得到的密文："<<endl;
    puts(str);
    cout<<"反解密得到的明文："<<endl;
    Des_Run(str,str,1);
    puts(str);
	
    return 0;
	
}

測試結果

基礎測試測試正確與否:

ECB模式測試：