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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 };
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