基于C++的DES加密算法实现代码实例

核心提示：今天偶尔想到数据加密技术，这里顺便提一下双向加密的标准DES.以前在一个宽带流媒体服务器项目中用到了DES加密，基于C++的DES加密算法实现代码实例，虽然使用环境相对单纯，但算法实现本身是具有普遍意义的，稳定性较好，便一直在实践中使用，下述程序是很久以前在RSA公司的网站找到的，效率很高

今天偶尔想到数据加密技术，这里顺便提一下双向加密的标准DES.以前在一个宽带流媒体服务器项目中用到了DES加密，虽然使用环境相对单纯，但算法实现本身是具有普遍意义的。下述程序是很久以前在RSA公司的网站找到的，效率很高，稳定性较好，便一直在实践中使用。

首先在头文件中定义一个DES类：　 //des.h

#ifndef __DES_H
#define __DES_H
class DES{
public:
　　　 // Encrypt/decrypt the data in "data", according to the "key".
　　　 // Caller is responsible for confirming the buffer size of "data"
　　　 // points to is 8*"blocks" bytes.
　　　 // The data encrypted/decrypted is stored in data.
　　　 // The return code is 1:success, other:failed.

　　　 int encrypt ( unsigned char key[8], unsigned char* data, int blocks = 1 );
　　　 int decrypt ( unsigned char key[8], unsigned char* data, int blocks = 1 );

　　　 // Encrypt/decrypt any size data,according to a special method.
　　　 // Before calling yencrypt, copy data to a new buffer with size
　　　 // calculated by extend.

　　　 int yencrypt ( unsigned char key[8], unsigned char* data, int size );
　　　 int ydecrypt ( unsigned char key[8], unsigned char* in, int blocks, int* size = 0 );
　　　 int extend ( int size ) { return (size/8+1)*8; };

private:
　　　 void des(unsigned char* in, unsigned char* out, int blocks);
　　　 void des_block(unsigned char* in, unsigned char* out);

private:
　　　 unsigned long KnL[32];
　　　 enum Mode { ENCRYPT, DECRYPT };
　　　 void deskey(unsigned char key[8], Mode md);
　　　 void usekey(unsigned long *);
　　　 void cookey(unsigned long *);

private:
　　　 void scrunch(unsigned char *, unsigned long *);
　　　 void unscrun(unsigned long *, unsigned char *);
　　　 void desfunc(unsigned long *, unsigned long *);

private:
　　　 static unsigned char Df_Key[24];
　　　 static unsigned short bytebit[8];
　　　 static unsigned long bigbyte[24];
　　　 static unsigned char pc1[56];
　　　 static unsigned char totrot[16];
　　　 static unsigned char pc2[48];
　　　 static unsigned long SP1[64];
　　　 static unsigned long SP2[64];
　　　 static unsigned long SP3[64];
　　　 static unsigned long SP4[64];
　　　 static unsigned long SP5[64];
　　　 static unsigned long SP6[64];
　　　 static unsigned long SP7[64];
　　　 static unsigned long SP8[64];
};
#endif

而后，具体实现DES类：

//des.cpp

#include <string.h>
#include "Sinodes.h"

int DES::encrypt ( unsigned char key[8], unsigned char* data, int blocks )
{
　 if ((!data)||(blocks<1))
　　　　　 return 0;
　 deskey ( key, ENCRYPT );
　 des ( data, data, blocks);
　 return 1;
};

int DES::decrypt ( unsigned char key[8], unsigned char* data, int blocks )
{
　 if ((!data)||(blocks<1))
　　　　　 return 0;
　 deskey ( key, DECRYPT );
　 des ( data, data, blocks);
　 return 1;
};

int DES::yencrypt ( unsigned char key[8], unsigned char* data, int size )
{
　 if ((!data)||(size<1))
　　　 return 0;

　 // The last char of data is bitwise complemented and filled the rest
　 // buffer.If size is 16, it will extend to 24,and 17 still 24.
　 char lastChar = *(data+size-1);
　 int blocks = size/8+1;
　 memset(data+size, ~lastChar, blocks*8-size);
　 deskey( key, ENCRYPT );
　 return encrypt ( data, data, blocks);
};

int DES::ydecrypt ( unsigned char key[8], unsigned char* data, int blocks, int* size )
{
　 if ( (!data) || (blocks<1) )
　　　 return 0;

　 deskey ( key, DECRYPT );
　 if ( !decrypt ( data, data, blocks) )
　　　 return 0;
　 if ( size != 0 )
　 {
　　　 int pos = blocks*8-1;
　　　 char endChar = data[pos];
　　　 while ((pos>0)&&(data[pos]==endChar))
　　　　　　　 pos--;
　　　 if ( data[pos] != ~endChar )
　　　　　 return 0;
　　　 *size = pos+1;
　 }
　 return 1;
};

// -----------------------------------------------------------------------
// des
//　　　　 Encrpts/Decrypts(according to the key currently loaded int the
//　　　　 internal key register) SOME blocks of eight bytes at address 'in'
//　　　　 into the block at address 'out'. They can be the same.
//
//　　　　 "in"
//　　　　 "out"
//　　　　 "block" Number of blocks.
// -----------------------------------------------------------------------
void DES::des ( unsigned char* in, unsigned char* out, int blocks )
{
for (int i = 0; i < blocks; i++,in+=8,out+=8)
　　　 des_block(in,out);
};

// -----------------------------------------------------------------------
// des_block
//　　　　 Encrpts/Decrypts(according to the key currently loaded int the
//　　　　 internal key register) one block of eight bytes at address 'in'
//　　　　 into the block at address 'out'. They can be the same.
//
//　　　　 "in"
//　　　　 "out"
// -----------------------------------------------------------------------
void DES::des_block(unsigned char *in, unsigned char *out)
{
unsigned long work[2];

scrunch(in, work);
desfunc(work, KnL);
unscrun(work, out);
};

// ----------------------------------------------------------------------
// deskey
//　　　　 Sets the internal key register (KnR) according to the hexadecimal
//　　　　 key contained in the 8 bytes of hexkey, according to the DES,
//　　　　 for encryption or decrytion according to MODE
//
//　　　　 "key" is the 64 bits key.
//　　　　 "md" means encryption or decryption.
// ----------------------------------------------------------------------
void DES::deskey(unsigned char key[8], Mode md)
{
register int ii, j, l, m, n;
unsigned char pc1m[56], pcr[56];
unsigned long kn[32];

for (j = 0; j < 56; j++) {
　 l = pc1[j];
　 m = l & 07;
　 pc1m[j] = (key[l >> 3] & bytebit[m]) ? 1:0;
}
for (ii = 0; ii < 16; ii++) {
　 if (md == DECRYP) m = (15 - ii) << 1;
　　　 else m = ii << 1;
　　　 n = m + 1;
　　　 kn[m] = kn[n] = 0L;
　　　 for (j = 0; j < 28; j++) {
　　　 l = j + totrot[ii];
　　　 if (l < 28) pcr[j] = pc1m[l];
　　　　　 else pcr[j] = pc1m[l - 28];
　　　 }
　　　 for (j = 28; j < 56; j++) {
　　　 l = j + totrot[ii];
　　　 if (l < 56) pcr[j] = pc1m[l];
　　　　　 else pcr[j] = pc1m[l - 28];
　　　 }
　　　 for (j = 0; j < 24; j++) {
　　　 if (pcr[ pc2[j] ]) kn[m] |= bigbyte[j];
　　　 if (pcr[ pc2[j+24] ]) kn[n] |= bigbyte[j];
　　　 }
}
cookey(kn);
return;
};

// ----------------------------------------------------------------------
// cookey
//　　　　 Only called by deskey.
// -----------------------------------------------------------------------
void DES::cookey(register unsigned long *raw1)
{
register unsigned long *cook, *raw0;
unsigned long dough[32];
register int i;

cook = dough;
for (i = 0; i < 16; i++, raw1++) {
　 raw0 = raw1++;
　 *cook = (*raw0 & 0x00fc0000L) << 6;
　 *cook |= (*raw0 & 0x00000fc0L) << 10;
　 *cook |= (*raw1 & 0x00fc0000L) >> 10;
　 *cook++ |= (*raw1 & 0x00000fc0L) >> 6;
　 *cook = (*raw0 & 0x0003f000L) << 12;
　 *cook |= (*raw0 & 0x0000003fL) << 16;
　 *cook |= (*raw1 & 0x0003f000L) >> 4;
　 *cook++ |= (*raw1 & 0x0000003fL);
}
usekey(dough);
return;
};

// ----------------------------------------------------------------------
// usekey
//　　　　 Only called by cookey.
//　　　　 Loads the interal key register with the data in cookedkey.
// -----------------------------------------------------------------------
void DES::usekey(register unsigned long *from)
{
register unsigned long *to, *endp;

to = KnL, endp = &KnL[32];
while (to < endp) *to++ = *from++;
return;
};

void DES::scrunch(register unsigned char *outof, register unsigned long *into )
{
*into = (*outof++ & 0xffL) << 24;
*into |= (*outof++ & 0xffL) << 16;
*into |= (*outof++ & 0xffL) << 8;
*into++ |= (*outof++ & 0xffL);
*into = (*outof++ & 0xffL) << 24;
*into |= (*outof++ & 0xffL) << 16;
*into |= (*outof++ & 0xffL) << 8;
*into |= (*outof & 0xffL);
return;
};

void DES::unscrun(register unsigned long *outof, register unsigned char *into)
{
*into++ = (*outof >> 24) & 0xffL;
*into++ = (*outof >> 16) & 0xffL;
*into++ = (*outof >> 8) & 0xffL;
*into++ = *outof++ & 0xffL;
*into++ = (*outof >> 24) & 0xffL;
*into++ = (*outof >> 16) & 0xffL;
*into++ = (*outof >> 8) & 0xffL;
*into = *outof & 0xffL;
return;
};

void DES::desfunc(register unsigned long *block,register unsigned long *keys)
{
register unsigned long fval, work, right, leftt;
register int round;

leftt = block[0];
right = block[1];
work = ((leftt >> 4) ^ right) & 0x0f0f0f0fL;
right ^= work;
leftt ^= (work << 4);
work = ((leftt >> 16) ^ right) & 0x0000ffffL;
right ^= work;
leftt ^= (work << 16);
work = ((right >> 2) ^ leftt) & 0x33333333L;
leftt ^= work;
right ^= (work << 2);
work = ((right >> 8) ^ leftt) & 0x00ff00ffL;
leftt ^= work;
right ^= (work << 8);
right = ((right << 1) | ((right >> 31) & 1L)) & 0xffffffffL;
work = (leftt ^ right) & 0xaaaaaaaaL;
leftt ^= work;
right ^= work;
leftt = ((leftt << 1) | ((leftt >> 31) & 1L)) & 0xffffffffL;

for (round = 0; round < 8; round++) {
　　　 work = (right << 28) | (right >> 4);
　　　 work ^= *keys++;
　　　 fval = SP7[work　　　　　　 & 0x3fL];
　　　 fval |= SP5[(work >> 8) & 0x3fL];
　　　 fval |= SP3[(work >> 16) & 0x3fL];
　　　 fval |= SP1[(work >> 24) & 0x3fL];
　　　 work = right ^ *keys++;
　　　 fval |= SP8[work　　　　　　 & 0x3fL];
　　　 fval |= SP6[(work >> 8) & 0x3fL];
　　　 fval |= SP4[(work >> 16) & 0x3fL];
　　　 fval |= SP2[(work >> 24) & 0x3fL];
　　　 leftt ^= fval;
　　　 work = (leftt << 28) | (leftt >> 4);
　　　 work ^= *keys++;
　　　 fval = SP7[work　　　　　　 & 0x3fL];
　　　 fval |= SP5[(work >> 8) & 0x3fL];
　　　 fval |= SP3[(work >> 16) & 0x3fL];
　　　 fval |= SP1[(work >> 24) & 0x3fL];
　　　 work = leftt ^ *keys++;
　　　 fval |= SP8[work　　　　　　 & 0x3fL];
　　　 fval |= SP6[(work >> 8) & 0x3fL];
　　　 fval |= SP4[(work >> 16) & 0x3fL];
　 fval |= SP2[(work >> 24) & 0x3fL];
　 right ^= fval;
}
right = (right << 31) | (right >> 1);
work = (leftt ^ right) & 0xaaaaaaaaL;
leftt ^= work;
right ^= work;
leftt = (leftt << 31) | ( leftt >> 1);
work = ((leftt >> 8) ^ right) & 0x00ff00ffL;
right ^= work;
leftt ^= (work << 8);
work = ((leftt >> 2) ^ right) & 0x33333333L;
right ^= work;
leftt ^= (work << 2);
work = ((right >> 16) ^ leftt) & 0x0000ffffL;
leftt ^= work;
right ^= (work << 16);
work = ((right >> 4) ^ leftt) & 0x0f0f0f0fL;
leftt ^= work;
right ^= (work << 4);
*block++ = right;
*block = leftt;
return;
};
// -----------------------------------------------------------------------
// Initial of static data members. These data will be used by all the
// instances of class,and can not be changed.
// -----------------------------------------------------------------------
unsigned char DES::Df_Key[24] = {
　　　 0x01, 0x23, 0x45, 0x67, 0x89, 0xab, 0xcd, 0xef,
　　　 0xfe, 0xdc, 0xba, 0x98, 0x76, 0x54, 0x32, 0x10,
　　　 0x89, 0xab, 0xcd, 0xef, 0x01, 0x23, 0x45, 0x67 };

unsigned short DES::bytebit[8] = {
　　　 0200, 0100, 040, 020, 010, 04, 02, 01 };

unsigned long DES::bigbyte[24] = {
　　　 0x800000L, 0x400000L, 0x200000L, 0x100000L,
　　　 0x80000L, 0x40000L, 0x20000L, 0x10000L,
　　　 0x8000L,　　 0x4000L,　　 0x2000L,　　 0x1000L,
　　　 0x800L,　　 0x400L,　　 0x200L,　　 0x100L,
　　　 0x80L,　　 0x40L,　　 0x20L,　　 0x10L,
　　　 0x8L,　　　　 0x4L,　　　　 0x2L,　　　　 0x1L　　　　 };

unsigned char DES::pc1[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　　 };

unsigned char DES::totrot[16] = {
　　　 1, 2, 4, 6, 8, 10, 12, 14, 15, 17, 19, 21, 23, 25, 27, 28 };

unsigned char DES::pc2[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, 47,
　　　 43, 48, 38, 55, 33, 52,　　 45, 41, 49, 35, 28, 31　　 };