心曲沉烟，悄望雪云平

今天偶尔想到数据加密技术，刚才简单讨论了一下MD5和SHA，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 "des.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   };

unsigned long DES::SP1[64] = {
  0x01010400L, 0x00000000L, 0x00010000L, 0x01010404L,
  0x01010004L, 0x00010404L, 0x00000004L, 0x00010000L,
  0x00000400L, 0x01010400L, 0x01010404L, 0x00000400L,
  0x01000404L, 0x01010004L, 0x01000000L, 0x00000004L,
  0x00000404L, 0x01000400L, 0x01000400L, 0x00010400L,
  0x00010400L, 0x01010000L, 0x01010000L, 0x01000404L,
  0x00010004L, 0x01000004L, 0x01000004L, 0x00010004L,
  0x00000000L, 0x00000404L, 0x00010404L, 0x01000000L,
  0x00010000L, 0x01010404L, 0x00000004L, 0x01010000L,
  0x01010400L, 0x01000000L, 0x01000000L, 0x00000400L,
  0x01010004L, 0x00010000L, 0x00010400L, 0x01000004L,
  0x00000400L, 0x00000004L, 0x01000404L, 0x00010404L,
  0x01010404L, 0x00010004L, 0x01010000L, 0x01000404L,
  0x01000004L, 0x00000404L, 0x00010404L, 0x01010400L,
  0x00000404L, 0x01000400L, 0x01000400L, 0x00000000L,
  0x00010004L, 0x00010400L, 0x00000000L, 0x01010004L };

unsigned long DES::SP2[64] = {
  0x80108020L, 0x80008000L, 0x00008000L, 0x00108020L,
  0x00100000L, 0x00000020L, 0x80100020L, 0x80008020L,
  0x80000020L, 0x80108020L, 0x80108000L, 0x80000000L,
  0x80008000L, 0x00100000L, 0x00000020L, 0x80100020L,
  0x00108000L, 0x00100020L, 0x80008020L, 0x00000000L,
  0x80000000L, 0x00008000L, 0x00108020L, 0x80100000L,
  0x00100020L, 0x80000020L, 0x00000000L, 0x00108000L,
  0x00008020L, 0x80108000L, 0x80100000L, 0x00008020L,
  0x00000000L, 0x00108020L, 0x80100020L, 0x00100000L,
  0x80008020L, 0x80100000L, 0x80108000L, 0x00008000L,
  0x80100000L, 0x80008000L, 0x00000020L, 0x80108020L,
  0x00108020L, 0x00000020L, 0x00008000L, 0x80000000L,
  0x00008020L, 0x80108000L, 0x00100000L, 0x80000020L,
  0x00100020L, 0x80008020L, 0x80000020L, 0x00100020L,
  0x00108000L, 0x00000000L, 0x80008000L, 0x00008020L,
  0x80000000L, 0x80100020L, 0x80108020L, 0x00108000L };

unsigned long DES::SP3[64] = {
  0x00000208L, 0x08020200L, 0x00000000L, 0x08020008L,
  0x08000200L, 0x00000000L, 0x00020208L, 0x08000200L,
  0x00020008L, 0x08000008L, 0x08000008L, 0x00020000L,
  0x08020208L, 0x00020008L, 0x08020000L, 0x00000208L,
  0x08000000L, 0x00000008L, 0x08020200L, 0x00000200L,
  0x00020200L, 0x08020000L, 0x08020008L, 0x00020208L,
  0x08000208L, 0x00020200L, 0x00020000L, 0x08000208L,
  0x00000008L, 0x08020208L, 0x00000200L, 0x08000000L,
  0x08020200L, 0x08000000L, 0x00020008L, 0x00000208L,
  0x00020000L, 0x08020200L, 0x08000200L, 0x00000000L,
  0x00000200L, 0x00020008L, 0x08020208L, 0x08000200L,
  0x08000008L, 0x00000200L, 0x00000000L, 0x08020008L,
  0x08000208L, 0x00020000L, 0x08000000L, 0x08020208L,
  0x00000008L, 0x00020208L, 0x00020200L, 0x08000008L,
  0x08020000L, 0x08000208L, 0x00000208L, 0x08020000L,
  0x00020208L, 0x00000008L, 0x08020008L, 0x00020200L };

unsigned long DES::SP4[64] = {
  0x00802001L, 0x00002081L, 0x00002081L, 0x00000080L,
  0x00802080L, 0x00800081L, 0x00800001L, 0x00002001L,
  0x00000000L, 0x00802000L, 0x00802000L, 0x00802081L,
  0x00000081L, 0x00000000L, 0x00800080L, 0x00800001L,
  0x00000001L, 0x00002000L, 0x00800000L, 0x00802001L,
  0x00000080L, 0x00800000L, 0x00002001L, 0x00002080L,
  0x00800081L, 0x00000001L, 0x00002080L, 0x00800080L,
  0x00002000L, 0x00802080L, 0x00802081L, 0x00000081L,
  0x00800080L, 0x00800001L, 0x00802000L, 0x00802081L,
  0x00000081L, 0x00000000L, 0x00000000L, 0x00802000L,
  0x00002080L, 0x00800080L, 0x00800081L, 0x00000001L,
  0x00802001L, 0x00002081L, 0x00002081L, 0x00000080L,
  0x00802081L, 0x00000081L, 0x00000001L, 0x00002000L,
  0x00800001L, 0x00002001L, 0x00802080L, 0x00800081L,
  0x00002001L, 0x00002080L, 0x00800000L, 0x00802001L,
  0x00000080L, 0x00800000L, 0x00002000L, 0x00802080L };

unsigned long DES::SP5[64] = {
  0x00000100L, 0x02080100L, 0x02080000L, 0x42000100L,
  0x00080000L, 0x00000100L, 0x40000000L, 0x02080000L,
  0x40080100L, 0x00080000L, 0x02000100L, 0x40080100L,
  0x42000100L, 0x42080000L, 0x00080100L, 0x40000000L,
  0x02000000L, 0x40080000L, 0x40080000L, 0x00000000L,
  0x40000100L, 0x42080100L, 0x42080100L, 0x02000100L,
  0x42080000L, 0x40000100L, 0x00000000L, 0x42000000L,
  0x02080100L, 0x02000000L, 0x42000000L, 0x00080100L,
  0x00080000L, 0x42000100L, 0x00000100L, 0x02000000L,
  0x40000000L, 0x02080000L, 0x42000100L, 0x40080100L,
  0x02000100L, 0x40000000L, 0x42080000L, 0x02080100L,
  0x40080100L, 0x00000100L, 0x02000000L, 0x42080000L,
  0x42080100L, 0x00080100L, 0x42000000L, 0x42080100L,
  0x02080000L, 0x00000000L, 0x40080000L, 0x42000000L,
  0x00080100L, 0x02000100L, 0x40000100L, 0x00080000L,
  0x00000000L, 0x40080000L, 0x02080100L, 0x40000100L };

unsigned long DES::SP6[64] = {
  0x20000010L, 0x20400000L, 0x00004000L, 0x20404010L,
  0x20400000L, 0x00000010L, 0x20404010L, 0x00400000L,
  0x20004000L, 0x00404010L, 0x00400000L, 0x20000010L,
  0x00400010L, 0x20004000L, 0x20000000L, 0x00004010L,
  0x00000000L, 0x00400010L, 0x20004010L, 0x00004000L,
  0x00404000L, 0x20004010L, 0x00000010L, 0x20400010L,
  0x20400010L, 0x00000000L, 0x00404010L, 0x20404000L,
  0x00004010L, 0x00404000L, 0x20404000L, 0x20000000L,
  0x20004000L, 0x00000010L, 0x20400010L, 0x00404000L,
  0x20404010L, 0x00400000L, 0x00004010L, 0x20000010L,
  0x00400000L, 0x20004000L, 0x20000000L, 0x00004010L,
  0x20000010L, 0x20404010L, 0x00404000L, 0x20400000L,
  0x00404010L, 0x20404000L, 0x00000000L, 0x20400010L,
  0x00000010L, 0x00004000L, 0x20400000L, 0x00404010L,
  0x00004000L, 0x00400010L, 0x20004010L, 0x00000000L,
  0x20404000L, 0x20000000L, 0x00400010L, 0x20004010L };

unsigned long DES::SP7[64] = {
  0x00200000L, 0x04200002L, 0x04000802L, 0x00000000L,
  0x00000800L, 0x04000802L, 0x00200802L, 0x04200800L,
  0x04200802L, 0x00200000L, 0x00000000L, 0x04000002L,
  0x00000002L, 0x04000000L, 0x04200002L, 0x00000802L,
  0x04000800L, 0x00200802L, 0x00200002L, 0x04000800L,
  0x04000002L, 0x04200000L, 0x04200800L, 0x00200002L,
  0x04200000L, 0x00000800L, 0x00000802L, 0x04200802L,
  0x00200800L, 0x00000002L, 0x04000000L, 0x00200800L,
  0x04000000L, 0x00200800L, 0x00200000L, 0x04000802L,
  0x04000802L, 0x04200002L, 0x04200002L, 0x00000002L,
  0x00200002L, 0x04000000L, 0x04000800L, 0x00200000L,
  0x04200800L, 0x00000802L, 0x00200802L, 0x04200800L,
  0x00000802L, 0x04000002L, 0x04200802L, 0x04200000L,
  0x00200800L, 0x00000000L, 0x00000002L, 0x04200802L,
  0x00000000L, 0x00200802L, 0x04200000L, 0x00000800L,
  0x04000002L, 0x04000800L, 0x00000800L, 0x00200002L };

unsigned long DES::SP8[64] = {
  0x10001040L, 0x00001000L, 0x00040000L, 0x10041040L,
  0x10000000L, 0x10001040L, 0x00000040L, 0x10000000L,
  0x00040040L, 0x10040000L, 0x10041040L, 0x00041000L,
  0x10041000L, 0x00041040L, 0x00001000L, 0x00000040L,
  0x10040000L, 0x10000040L, 0x10001000L, 0x00001040L,
  0x00041000L, 0x00040040L, 0x10040040L, 0x10041000L,
  0x00001040L, 0x00000000L, 0x00000000L, 0x10040040L,
  0x10000040L, 0x10001000L, 0x00041040L, 0x00040000L,
  0x00041040L, 0x00040000L, 0x10041000L, 0x00001000L,
  0x00000040L, 0x10040040L, 0x00001000L, 0x00041040L,
  0x10001000L, 0x00000040L, 0x10000040L, 0x10040000L,
  0x10040040L, 0x10000000L, 0x00040000L, 0x10001040L,
  0x00000000L, 0x10041040L, 0x00040040L, 0x10000040L,
  0x10040000L, 0x10001000L, 0x10001040L, 0x00000000L,
  0x10041040L, 0x00041000L, 0x00041000L, 0x00001040L,
  0x00001040L, 0x00040040L, 0x10000000L, 0x10041000L };


接下来我们举例说明如何使用DES类。首先定义一个Encrypt类：


//Encrypt.h

#include "des.h"
#include "Base64.h"
class Encrypt{
public :  
  char* encrypt ( unsigned char key[8], char* data);
  char* decrypt ( unsigned char key[8], char* data);
  CBase64 base;
};


而后是具体的实现：

//Encrypt.cpp

#include "Encrypt.h"
#include <stdio.h>

char* Encrypt::encrypt ( unsigned char key[8], char* data)
{
//将字符指针转化为字符数组
  char* datavv = data;
  data =(char *) calloc(100,1);
  memcpy(data,datavv,strlen(datavv));
  data[strlen(data)] = '\0';
//DES加密  
  DES des ;
  des.encrypt(key,(unsigned char *)data,1);  
//base64编码
  base.Encode(data);
  char* res =(char *) base.EncodedMessage();
  return res;
};
char* Encrypt::decrypt ( unsigned char key[8], char* data)
{
//base64解码
  base.Decode(data);
  char* datares=(char *) base.DecodedMessage();
//将字符指针转化为字符数组
  char* datarea = datares;
  datares = (char *)malloc(256);
  memcpy(datares,datarea,strlen(datarea));
  datares[strlen(datarea)] = '\0';
//DES解密
  DES des ;
  des.decrypt(key,(unsigned char*) datares,1);
  return datares;
};


注意，这里使用了BASE 64编码。其实现代码如下：

// Base64.h
#include <windows.h>

class CBase64
{
  // Internal bucket class.
  class TempBucket
  {
  public:
    BYTE       nData[4];
    BYTE       nSize;
    void       Clear() { ::ZeroMemory(nData, 4); nSize = 0; };
  };

  PBYTE               m_pDBuffer;
  PBYTE               m_pEBuffer;
  DWORD               m_nDBufLen;
  DWORD               m_nEBufLen;
  DWORD               m_nDDataLen;
  DWORD               m_nEDataLen;

public:
  CBase64();
  virtual ~CBase64();

public:
  virtual void       Encode(const PBYTE, DWORD);
  virtual void       Decode(const PBYTE, DWORD);
  virtual void       Encode(LPCSTR sMessage);
  virtual void       Decode(LPCSTR sMessage);

  virtual LPCSTR   DecodedMessage() const;
  virtual LPCSTR   EncodedMessage() const;

  virtual void       AllocEncode(DWORD);
  virtual void       AllocDecode(DWORD);
  virtual void       SetEncodeBuffer(const PBYTE pBuffer, DWORD nBufLen);
  virtual void       SetDecodeBuffer(const PBYTE pBuffer, DWORD nBufLen);

protected:
  virtual void       _EncodeToBuffer(const TempBucket &Decode, PBYTE pBuffer);
  virtual ULONG       _DecodeToBuffer(const TempBucket &Decode, PBYTE pBuffer);
  virtual void       _EncodeRaw(TempBucket &, const TempBucket &);
  virtual void       _DecodeRaw(TempBucket &, const TempBucket &);
  virtual BOOL       _IsBadMimeChar(BYTE);

  static char       m_DecodeTable[256];
  static BOOL       m_Init;
  void               _Init();
};
////////////////////////////////////

//CBase64.cpp
// CBase64.cpp: implementation of the CBase64 class.
//
//////////////////////////////////////////////////////////////////////

#include "Base64.h"

// Digits...
static char Base64Digits[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

BOOL CBase64::m_Init   = FALSE;
char CBase64::m_DecodeTable[256];

#ifndef PAGESIZE
#define PAGESIZE     4096
#endif

#ifndef ROUNDTOPAGE
#define ROUNDTOPAGE(a)   (((a/4096)+1)*4096)
#endif

//////////////////////////////////////////////////////////////////////
// Construction/Destruction
//////////////////////////////////////////////////////////////////////

CBase64::CBase64()
: m_pDBuffer(NULL),
m_pEBuffer(NULL),
m_nDBufLen(0),
m_nEBufLen(0)
{

}

CBase64::~CBase64()
{
if(m_pDBuffer != NULL)
delete [] m_pDBuffer;

if(m_pEBuffer != NULL)
delete [] m_pEBuffer;
}

LPCSTR CBase64::DecodedMessage() const
{
return (LPCSTR) m_pDBuffer;
}

LPCSTR CBase64::EncodedMessage() const
{
return (LPCSTR) m_pEBuffer;
}

void CBase64::AllocEncode(DWORD nSize)
{
if(m_nEBufLen < nSize)
{
if(m_pEBuffer != NULL)
  delete [] m_pEBuffer;

m_nEBufLen = ROUNDTOPAGE(nSize);
m_pEBuffer = new BYTE[m_nEBufLen];
}

::ZeroMemory(m_pEBuffer, m_nEBufLen);
m_nEDataLen = 0;
}

void CBase64::AllocDecode(DWORD nSize)
{
if(m_nDBufLen < nSize)
{
if(m_pDBuffer != NULL)
  delete [] m_pDBuffer;

m_nDBufLen = ROUNDTOPAGE(nSize);
m_pDBuffer = new BYTE[m_nDBufLen];
}

::ZeroMemory(m_pDBuffer, m_nDBufLen);
m_nDDataLen = 0;
}

void CBase64::SetEncodeBuffer(const PBYTE pBuffer, DWORD nBufLen)
{
DWORD ii = 0;

AllocEncode(nBufLen);
while(ii < nBufLen)
{
if(!_IsBadMimeChar(pBuffer[ii]))
{
  m_pEBuffer[m_nEDataLen] = pBuffer[ii];
  m_nEDataLen++;
}

ii++;
}
}

void CBase64::SetDecodeBuffer(const PBYTE pBuffer, DWORD nBufLen)
{
AllocDecode(nBufLen);
::CopyMemory(m_pDBuffer, pBuffer, nBufLen);
m_nDDataLen = nBufLen;
}

void CBase64::Encode(const PBYTE pBuffer, DWORD nBufLen)
{
SetDecodeBuffer(pBuffer, nBufLen);
AllocEncode(nBufLen * 2);

TempBucket   Raw;
DWORD     nIndex = 0;

while((nIndex + 3) <= nBufLen)
{
Raw.Clear();
::CopyMemory(&Raw, m_pDBuffer + nIndex, 3);
Raw.nSize = 3;
_EncodeToBuffer(Raw, m_pEBuffer + m_nEDataLen);
nIndex   += 3;
m_nEDataLen += 4;
}

if(nBufLen > nIndex)
{
Raw.Clear();
Raw.nSize = (BYTE) (nBufLen - nIndex);
::CopyMemory(&Raw, m_pDBuffer + nIndex, nBufLen - nIndex);
_EncodeToBuffer(Raw, m_pEBuffer + m_nEDataLen);
m_nEDataLen += 4;
}
}

void CBase64::Encode(LPCSTR szMessage)
{
if(szMessage != NULL)
CBase64::Encode((const PBYTE)szMessage, lstrlenA(szMessage));
}

void CBase64::Decode(const PBYTE pBuffer, DWORD dwBufLen)
{
if(!CBase64::m_Init)
_Init();

SetEncodeBuffer(pBuffer, dwBufLen);

AllocDecode(dwBufLen);

TempBucket   Raw;

DWORD   nIndex = 0;

while((nIndex + 4) <= m_nEDataLen)
{
Raw.Clear();
Raw.nData[0] = CBase64::m_DecodeTable[m_pEBuffer[nIndex]];
Raw.nData[1] = CBase64::m_DecodeTable[m_pEBuffer[nIndex + 1]];
Raw.nData[2] = CBase64::m_DecodeTable[m_pEBuffer[nIndex + 2]];
Raw.nData[3] = CBase64::m_DecodeTable[m_pEBuffer[nIndex + 3]];

if(Raw.nData[2] == 255)
  Raw.nData[2] = 0;
if(Raw.nData[3] == 255)
  Raw.nData[3] = 0;

Raw.nSize = 4;
_DecodeToBuffer(Raw, m_pDBuffer + m_nDDataLen);
nIndex += 4;
m_nDDataLen += 3;
}

// If nIndex < m_nEDataLen, then we got a decode message without padding.
// We may want to throw some kind of warning here, but we are still required
// to handle the decoding as if it was properly padded.
if(nIndex < m_nEDataLen)
{
Raw.Clear();
for(DWORD ii = nIndex; ii < m_nEDataLen; ii++)
{
  Raw.nData[ii - nIndex] = CBase64::m_DecodeTable[m_pEBuffer[ii]];
  Raw.nSize++;
  if(Raw.nData[ii - nIndex] == 255)
  Raw.nData[ii - nIndex] = 0;
}

_DecodeToBuffer(Raw, m_pDBuffer + m_nDDataLen);
m_nDDataLen += (m_nEDataLen - nIndex);
}
}

void CBase64::Decode(LPCSTR szMessage)
{
if(szMessage != NULL)
CBase64::Decode((const PBYTE)szMessage, lstrlenA(szMessage));
}

DWORD CBase64::_DecodeToBuffer(const TempBucket &Decode, PBYTE pBuffer)
{
TempBucket Data;
DWORD   nCount = 0;

_DecodeRaw(Data, Decode);

for(int ii = 0; ii < 3; ii++)
{
pBuffer[ii] = Data.nData[ii];
if(pBuffer[ii] != 255)
  nCount++;
}

return nCount;
}


void CBase64::_EncodeToBuffer(const TempBucket &Decode, PBYTE pBuffer)
{
TempBucket Data;

_EncodeRaw(Data, Decode);

for(int ii = 0; ii < 4; ii++)
pBuffer[ii] = Base64Digits[Data.nData[ii]];

switch(Decode.nSize)
{
case 1:
pBuffer[2] = '=';
case 2:
pBuffer[3] = '=';
}
}

void CBase64::_DecodeRaw(TempBucket &Data, const TempBucket &Decode)
{
BYTE   nTemp;

Data.nData[0] = Decode.nData[0];
Data.nData[0] <<= 2;

nTemp = Decode.nData[1];
nTemp >>= 4;
nTemp &= 0x03;
Data.nData[0] |= nTemp;

Data.nData[1] = Decode.nData[1];
Data.nData[1] <<= 4;

nTemp = Decode.nData[2];
nTemp >>= 2;
nTemp &= 0x0F;
Data.nData[1] |= nTemp;

Data.nData[2] = Decode.nData[2];
Data.nData[2] <<= 6;
nTemp = Decode.nData[3];
nTemp &= 0x3F;
Data.nData[2] |= nTemp;
}

void CBase64::_EncodeRaw(TempBucket &Data, const TempBucket &Decode)
{
BYTE   nTemp;

Data.nData[0] = Decode.nData[0];
Data.nData[0] >>= 2;

Data.nData[1] = Decode.nData[0];
Data.nData[1] <<= 4;
nTemp = Decode.nData[1];
nTemp >>= 4;
Data.nData[1] |= nTemp;
Data.nData[1] &= 0x3F;

Data.nData[2] = Decode.nData[1];
Data.nData[2] <<= 2;

nTemp = Decode.nData[2];
nTemp >>= 6;

Data.nData[2] |= nTemp;
Data.nData[2] &= 0x3F;

Data.nData[3] = Decode.nData[2];
Data.nData[3] &= 0x3F;
}

BOOL CBase64::_IsBadMimeChar(BYTE nData)
{
switch(nData)
{
case '\r': case '\n': case '\t': case ' ' :
case '\b': case '\a': case '\f': case '\v':
return TRUE;
default:
return FALSE;
}
}

void CBase64::_Init()
{ // Initialize Decoding table.

int ii;

for(ii = 0; ii < 256; ii++)
CBase64::m_DecodeTable[ii] = -2;

for(ii = 0; ii < 64; ii++)
{
CBase64::m_DecodeTable[Base64Digits[ii]]   = (CHAR)ii;
CBase64::m_DecodeTable[Base64Digits[ii]|0x80] = (CHAR)ii;
}

CBase64::m_DecodeTable['=']   = -1;
CBase64::m_DecodeTable['='|0x80]   = -1;

CBase64::m_Init = TRUE;
}