//對字段進行加密

CString MD_password,MD_name,MD_email;
//調用加密函數
MD_name = CMD5Checksum::GetMD5(name);
MD_password = CMD5Checksum::GetMD5(password);
MD_email = CMD5Checksum::GetMD5(email);

其中GetMD5函數就是完成對字符串的加密工作。這個函數保存在MD5Checksum.h和MD5ChecksumDefines.h里，函數的實現在MD5Checksum.cpp文件里。可以完成對字符串的加密，還可以完成對文件名的加密工作。這三個文件如下：

MD5Checksum.h:

#if !defined(AFX_MD5CHECKSUM_H__2BC7928E_4C15_11D3_B2EE_A4A60E20D2C3__INCLUDED_)
#define AFX_MD5CHECKSUM_H__2BC7928E_4C15_11D3_B2EE_A4A60E20D2C3__INCLUDED_

#if _MSC_VER > 1000
#pragma once

#endif // _MSC_VER > 1000

class CMD5Checksum
{
public:
//interface functions for the RSA MD5 calculation
static CString GetMD5(BYTE* pBuf, UINT nLength);
static CString GetMD5(CFile& File);
//static CString GetMD5(const CString& strFilePath);//對文件名加密
static CString GetMD5(const CString str);//對字符串加密

protected:
//constructor/destructor
CMD5Checksum();
virtual ~CMD5Checksum() {};

//RSA MD5 implementation
void Transform(BYTE Block[64]);
void Update(BYTE* Input, ULONG nInputLen);
CString Final();
inline DWORD RotateLeft(DWORD x, int n);
inline void FF( DWORD& A, DWORD B, DWORD C, DWORD D, DWORD X, DWORD S, DWORD T);
inline void GG( DWORD& A, DWORD B, DWORD C, DWORD D, DWORD X, DWORD S, DWORD T);
inline void HH( DWORD& A, DWORD B, DWORD C, DWORD D, DWORD X, DWORD S, DWORD T);
inline void II( DWORD& A, DWORD B, DWORD C, DWORD D, DWORD X, DWORD S, DWORD T);

//utility functions
void DWordToByte(BYTE* Output, DWORD* Input, UINT nLength);
void ByteToDWord(DWORD* Output, BYTE* Input, UINT nLength);

private:
BYTE m_lpszBuffer[64]; //input buffer
ULONG m_nCount[2]; //number of bits, modulo 2^64 (lsb first)
ULONG m_lMD5[4]; //MD5 checksum
};

#endif // !defined(AFX_MD5CHECKSUM_H__2BC7928E_4C15_11D3_B2EE_A4A60E20D2C3__INCLUDED_)

MD5ChecksumDefines.h

//MD5ChecksumDefines.h : MD5 Checksum constants

//Magic initialization constants
#define MD5_INIT_STATE_0 0x67452301
#define MD5_INIT_STATE_1 0xefcdab89
#define MD5_INIT_STATE_2 0x98badcfe
#define MD5_INIT_STATE_3 0x10325476

//Constants for Transform routine.
#define MD5_S11 7
#define MD5_S12 12
#define MD5_S13 17
#define MD5_S14 22
#define MD5_S21 5
#define MD5_S22 9
#define MD5_S23 14
#define MD5_S24 20
#define MD5_S31 4
#define MD5_S32 11
#define MD5_S33 16
#define MD5_S34 23
#define MD5_S41 6
#define MD5_S42 10
#define MD5_S43 15
#define MD5_S44 21

//Transformation Constants - Round 1
#define MD5_T01 0xd76aa478 //Transformation Constant 1
#define MD5_T02 0xe8c7b756 //Transformation Constant 2
#define MD5_T03 0x242070db //Transformation Constant 3
#define MD5_T04 0xc1bdceee //Transformation Constant 4
#define MD5_T05 0xf57c0faf //Transformation Constant 5
#define MD5_T06 0x4787c62a //Transformation Constant 6
#define MD5_T07 0xa8304613 //Transformation Constant 7
#define MD5_T08 0xfd469501 //Transformation Constant 8
#define MD5_T09 0x698098d8 //Transformation Constant 9
#define MD5_T10 0x8b44f7af //Transformation Constant 10
#define MD5_T11 0xffff5bb1 //Transformation Constant 11
#define MD5_T12 0x895cd7be //Transformation Constant 12
#define MD5_T13 0x6b901122 //Transformation Constant 13
#define MD5_T14 0xfd987193 //Transformation Constant 14
#define MD5_T15 0xa679438e //Transformation Constant 15
#define MD5_T16 0x49b40821 //Transformation Constant 16

//Transformation Constants - Round 2
#define MD5_T17 0xf61e2562 //Transformation Constant 17
#define MD5_T18 0xc040b340 //Transformation Constant 18
#define MD5_T19 0x265e5a51 //Transformation Constant 19
#define MD5_T20 0xe9b6c7aa //Transformation Constant 20
#define MD5_T21 0xd62f105d //Transformation Constant 21
#define MD5_T22 0x02441453 //Transformation Constant 22
#define MD5_T23 0xd8a1e681 //Transformation Constant 23
#define MD5_T24 0xe7d3fbc8 //Transformation Constant 24
#define MD5_T25 0x21e1cde6 //Transformation Constant 25
#define MD5_T26 0xc33707d6 //Transformation Constant 26
#define MD5_T27 0xf4d50d87 //Transformation Constant 27
#define MD5_T28 0x455a14ed //Transformation Constant 28
#define MD5_T29 0xa9e3e905 //Transformation Constant 29
#define MD5_T30 0xfcefa3f8 //Transformation Constant 30
#define MD5_T31 0x676f02d9 //Transformation Constant 31
#define MD5_T32 0x8d2a4c8a //Transformation Constant 32

//Transformation Constants - Round 3
#define MD5_T33 0xfffa3942 //Transformation Constant 33
#define MD5_T34 0x8771f681 //Transformation Constant 34
#define MD5_T35 0x6d9d6122 //Transformation Constant 35
#define MD5_T36 0xfde5380c //Transformation Constant 36
#define MD5_T37 0xa4beea44 //Transformation Constant 37
#define MD5_T38 0x4bdecfa9 //Transformation Constant 38
#define MD5_T39 0xf6bb4b60 //Transformation Constant 39
#define MD5_T40 0xbebfbc70 //Transformation Constant 40
#define MD5_T41 0x289b7ec6 //Transformation Constant 41
#define MD5_T42 0xeaa127fa //Transformation Constant 42
#define MD5_T43 0xd4ef3085 //Transformation Constant 43
#define MD5_T44 0x04881d05 //Transformation Constant 44
#define MD5_T45 0xd9d4d039 //Transformation Constant 45
#define MD5_T46 0xe6db99e5 //Transformation Constant 46
#define MD5_T47 0x1fa27cf8 //Transformation Constant 47
#define MD5_T48 0xc4ac5665 //Transformation Constant 48

//Transformation Constants - Round 4
#define MD5_T49 0xf4292244 //Transformation Constant 49
#define MD5_T50 0x432aff97 //Transformation Constant 50
#define MD5_T51 0xab9423a7 //Transformation Constant 51
#define MD5_T52 0xfc93a039 //Transformation Constant 52
#define MD5_T53 0x655b59c3 //Transformation Constant 53
#define MD5_T54 0x8f0ccc92 //Transformation Constant 54
#define MD5_T55 0xffeff47d //Transformation Constant 55
#define MD5_T56 0x85845dd1 //Transformation Constant 56
#define MD5_T57 0x6fa87e4f //Transformation Constant 57
#define MD5_T58 0xfe2ce6e0 //Transformation Constant 58
#define MD5_T59 0xa3014314 //Transformation Constant 59
#define MD5_T60 0x4e0811a1 //Transformation Constant 60
#define MD5_T61 0xf7537e82 //Transformation Constant 61
#define MD5_T62 0xbd3af235 //Transformation Constant 62
#define MD5_T63 0x2ad7d2bb //Transformation Constant 63
#define MD5_T64 0xeb86d391 //Transformation Constant 64

//Null data (except for first BYTE) used to finalise the checksum calculation
static unsigned char PADDING[64] = {
0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
};

MD5Checksum.cpp

// MD5Checksum.cpp: implementation of the MD5Checksum class.
//
//////////////////////////////////////////////////////////////////////

#include "stdafx.h"
#include "MD5Checksum.h"
#include "MD5ChecksumDefines.h"

#ifdef _DEBUG
#undef THIS_FILE
static char THIS_FILE[]=__FILE__;
#define new DEBUG_NEW
#endif

//CString CMD5Checksum::GetMD5(const CString& strFilePath)
//{
// //open the file as a binary file in readonly mode, denying write access
// CFile File(strFilePath, CFile::modeRead | CFile::shareDenyWrite | CFile::typeBinary);
//
// //the file has been successfully opened, so now get and return its checksum
// return GetMD5(File);
//}

CString CMD5Checksum::GetMD5(const CString str)
{
try
{
CMD5Checksum MD5Checksum; //checksum object
int nLength = 0; //number of bytes read from the file
const int nBufferSize = 1024; //checksum the file in blocks of 1024 bytes
BYTE Buffer[nBufferSize]; //buffer for data read from the file

//checksum the file in blocks of 1024 bytes
if((nLength = str.GetLength()) > 0 )
{
MD5Checksum.Update( Buffer, nLength );
}

//finalise the checksum and return it
return MD5Checksum.Final();
}

//report any file exceptions in debug mode only
catch (CFileException* e )
{
TRACE0("CMD5Checksum::GetMD5: CFileException caught");
throw e;
}
}

CString CMD5Checksum::GetMD5(CFile& File)
{
try
{
CMD5Checksum MD5Checksum; //checksum object
int nLength = 0; //number of bytes read from the file
const int nBufferSize = 1024; //checksum the file in blocks of 1024 bytes
BYTE Buffer[nBufferSize]; //buffer for data read from the file

//checksum the file in blocks of 1024 bytes
while ((nLength = File.Read( Buffer, nBufferSize )) > 0 )
{
MD5Checksum.Update( Buffer, nLength );
}

//finalise the checksum and return it
return MD5Checksum.Final();
}

//report any file exceptions in debug mode only
catch (CFileException* e )
{
TRACE0("CMD5Checksum::GetMD5: CFileException caught");
throw e;
}
}

CString CMD5Checksum::GetMD5(BYTE* pBuf, UINT nLength)
{
//entry invariants
// IsValidAddress(pBuf,nLength,FALSE);

//calculate and return the checksum
CMD5Checksum MD5Checksum;
MD5Checksum.Update( pBuf, nLength );
return MD5Checksum.Final();
}

DWORD CMD5Checksum::RotateLeft(DWORD x, int n)
{
//check that DWORD is 4 bytes long - true in Visual C++ 6 and 32 bit Windows
// sizeof(x);

//rotate and return x
return (x << n) | (x >> (32-n));
}

void CMD5Checksum::FF( DWORD& A, DWORD B, DWORD C, DWORD D, DWORD X, DWORD S, DWORD T)
{
DWORD F = (B & C) | (~B & D);
A += F + X + T;
A = RotateLeft(A, S);
A += B;
}

void CMD5Checksum::GG( DWORD& A, DWORD B, DWORD C, DWORD D, DWORD X, DWORD S, DWORD T)
{
DWORD G = (B & D) | (C & ~D);
A += G + X + T;
A = RotateLeft(A, S);
A += B;
}

void CMD5Checksum::HH( DWORD& A, DWORD B, DWORD C, DWORD D, DWORD X, DWORD S, DWORD T)
{
DWORD H = (B ^ C ^ D);
A += H + X + T;
A = RotateLeft(A, S);
A += B;
}

void CMD5Checksum::II( DWORD& A, DWORD B, DWORD C, DWORD D, DWORD X, DWORD S, DWORD T)
{
DWORD I = (C ^ (B | ~D));
A += I + X + T;
A = RotateLeft(A, S);
A += B;
}

void CMD5Checksum::ByteToDWord(DWORD* Output, BYTE* Input, UINT nLength)
{
//entry invariants
ASSERT( nLength % 4 == 0 );
ASSERT( AfxIsValidAddress(Output, nLength/4, TRUE) );
ASSERT( AfxIsValidAddress(Input, nLength, FALSE) );

//initialisations
UINT i=0; //index to Output array
UINT j=0; //index to Input array

//transfer the data by shifting and copying
for ( ; j < nLength; i++, j += 4)
{
Output[i] = (ULONG)Input[j] |
(ULONG)Input[j+1] << 8 |
(ULONG)Input[j+2] << 16 |
(ULONG)Input[j+3] << 24;
}
}

void CMD5Checksum::Transform(BYTE Block[64])
{
//initialise local data with current checksum
ULONG a = m_lMD5[0];
ULONG b = m_lMD5[1];
ULONG c = m_lMD5[2];
ULONG d = m_lMD5[3];

//copy BYTES from input 'Block' to an array of ULONGS 'X'
ULONG X[16];
ByteToDWord( X, Block, 64 );

//Perform Round 1 of the transformation
FF (a, b, c, d, X[ 0], MD5_S11, MD5_T01);
FF (d, a, b, c, X[ 1], MD5_S12, MD5_T02);
FF (c, d, a, b, X[ 2], MD5_S13, MD5_T03);
FF (b, c, d, a, X[ 3], MD5_S14, MD5_T04);
FF (a, b, c, d, X[ 4], MD5_S11, MD5_T05);
FF (d, a, b, c, X[ 5], MD5_S12, MD5_T06);
FF (c, d, a, b, X[ 6], MD5_S13, MD5_T07);
FF (b, c, d, a, X[ 7], MD5_S14, MD5_T08);
FF (a, b, c, d, X[ 8], MD5_S11, MD5_T09);
FF (d, a, b, c, X[ 9], MD5_S12, MD5_T10);
FF (c, d, a, b, X[10], MD5_S13, MD5_T11);
FF (b, c, d, a, X[11], MD5_S14, MD5_T12);
FF (a, b, c, d, X[12], MD5_S11, MD5_T13);
FF (d, a, b, c, X[13], MD5_S12, MD5_T14);
FF (c, d, a, b, X[14], MD5_S13, MD5_T15);
FF (b, c, d, a, X[15], MD5_S14, MD5_T16);

//Perform Round 2 of the transformation
GG (a, b, c, d, X[ 1], MD5_S21, MD5_T17);
GG (d, a, b, c, X[ 6], MD5_S22, MD5_T18);
GG (c, d, a, b, X[11], MD5_S23, MD5_T19);
GG (b, c, d, a, X[ 0], MD5_S24, MD5_T20);
GG (a, b, c, d, X[ 5], MD5_S21, MD5_T21);
GG (d, a, b, c, X[10], MD5_S22, MD5_T22);
GG (c, d, a, b, X[15], MD5_S23, MD5_T23);
GG (b, c, d, a, X[ 4], MD5_S24, MD5_T24);
GG (a, b, c, d, X[ 9], MD5_S21, MD5_T25);
GG (d, a, b, c, X[14], MD5_S22, MD5_T26);
GG (c, d, a, b, X[ 3], MD5_S23, MD5_T27);
GG (b, c, d, a, X[ 8], MD5_S24, MD5_T28);
GG (a, b, c, d, X[13], MD5_S21, MD5_T29);
GG (d, a, b, c, X[ 2], MD5_S22, MD5_T30);
GG (c, d, a, b, X[ 7], MD5_S23, MD5_T31);
GG (b, c, d, a, X[12], MD5_S24, MD5_T32);

//Perform Round 3 of the transformation
HH (a, b, c, d, X[ 5], MD5_S31, MD5_T33);
HH (d, a, b, c, X[ 8], MD5_S32, MD5_T34);
HH (c, d, a, b, X[11], MD5_S33, MD5_T35);
HH (b, c, d, a, X[14], MD5_S34, MD5_T36);
HH (a, b, c, d, X[ 1], MD5_S31, MD5_T37);
HH (d, a, b, c, X[ 4], MD5_S32, MD5_T38);
HH (c, d, a, b, X[ 7], MD5_S33, MD5_T39);
HH (b, c, d, a, X[10], MD5_S34, MD5_T40);
HH (a, b, c, d, X[13], MD5_S31, MD5_T41);
HH (d, a, b, c, X[ 0], MD5_S32, MD5_T42);
HH (c, d, a, b, X[ 3], MD5_S33, MD5_T43);
HH (b, c, d, a, X[ 6], MD5_S34, MD5_T44);
HH (a, b, c, d, X[ 9], MD5_S31, MD5_T45);
HH (d, a, b, c, X[12], MD5_S32, MD5_T46);
HH (c, d, a, b, X[15], MD5_S33, MD5_T47);
HH (b, c, d, a, X[ 2], MD5_S34, MD5_T48);

//Perform Round 4 of the transformation
II (a, b, c, d, X[ 0], MD5_S41, MD5_T49);
II (d, a, b, c, X[ 7], MD5_S42, MD5_T50);
II (c, d, a, b, X[14], MD5_S43, MD5_T51);
II (b, c, d, a, X[ 5], MD5_S44, MD5_T52);
II (a, b, c, d, X[12], MD5_S41, MD5_T53);
II (d, a, b, c, X[ 3], MD5_S42, MD5_T54);
II (c, d, a, b, X[10], MD5_S43, MD5_T55);
II (b, c, d, a, X[ 1], MD5_S44, MD5_T56);
II (a, b, c, d, X[ 8], MD5_S41, MD5_T57);
II (d, a, b, c, X[15], MD5_S42, MD5_T58);
II (c, d, a, b, X[ 6], MD5_S43, MD5_T59);
II (b, c, d, a, X[13], MD5_S44, MD5_T60);
II (a, b, c, d, X[ 4], MD5_S41, MD5_T61);
II (d, a, b, c, X[11], MD5_S42, MD5_T62);
II (c, d, a, b, X[ 2], MD5_S43, MD5_T63);
II (b, c, d, a, X[ 9], MD5_S44, MD5_T64);

//add the transformed values to the current checksum
m_lMD5[0] += a;
m_lMD5[1] += b;
m_lMD5[2] += c;
m_lMD5[3] += d;
}

CMD5Checksum::CMD5Checksum()
{
// zero members
memset( m_lpszBuffer, 0, 64 );
m_nCount[0] = m_nCount[1] = 0;

// Load magic state initialization constants
m_lMD5[0] = MD5_INIT_STATE_0;
m_lMD5[1] = MD5_INIT_STATE_1;
m_lMD5[2] = MD5_INIT_STATE_2;
m_lMD5[3] = MD5_INIT_STATE_3;
}

void CMD5Checksum::DWordToByte(BYTE* Output, DWORD* Input, UINT nLength )
{
//entry invariants
ASSERT( nLength % 4 == 0 );
ASSERT( AfxIsValidAddress(Output, nLength, TRUE) );
ASSERT( AfxIsValidAddress(Input, nLength/4, FALSE) );

//transfer the data by shifting and copying
UINT i = 0;
UINT j = 0;
for ( ; j < nLength; i++, j += 4)
{
Output[j] = (UCHAR)(Input[i] & 0xff);
Output[j+1] = (UCHAR)((Input[i] >> 8) & 0xff);
Output[j+2] = (UCHAR)((Input[i] >> 16) & 0xff);
Output[j+3] = (UCHAR)((Input[i] >> 24) & 0xff);
}
}

CString CMD5Checksum::Final()
{
//Save number of bits
BYTE Bits[8];
DWordToByte( Bits, m_nCount, 8 );

//Pad out to 56 mod 64.
UINT nIndex = (UINT)((m_nCount[0] >> 3) & 0x3f);
UINT nPadLen = (nIndex < 56) ? (56 - nIndex) : (120 - nIndex);
Update( PADDING, nPadLen );

//Append length (before padding)
Update( Bits, 8 );

//Store final state in 'lpszMD5'
const int nMD5Size = 16;
unsigned char lpszMD5[ nMD5Size ];
DWordToByte( lpszMD5, m_lMD5, nMD5Size );

//Convert the hexadecimal checksum to a CString
CString strMD5;
for ( int i=0; i < nMD5Size; i++)
{
CString Str;
if (lpszMD5[i] == 0) {
Str = CString("00");
}
else if (lpszMD5[i] <= 15) {
Str.Format(_T("0%x"),lpszMD5[i]);
}
else {
Str.Format(_T("%x"),lpszMD5[i]);
}

ASSERT( Str.GetLength() == 2 );
strMD5 += Str;
}
ASSERT( strMD5.GetLength() == 32 );
return strMD5;
}

void CMD5Checksum::Update( BYTE* Input, ULONG nInputLen )
{
//Compute number of bytes mod 64
UINT nIndex = (UINT)((m_nCount[0] >> 3) & 0x3F);

//Update number of bits
if ( ( m_nCount[0] += nInputLen << 3 ) < ( nInputLen << 3) )
{
m_nCount[1]++;
}
m_nCount[1] += (nInputLen >> 29);

//Transform as many times as possible.
UINT i=0;
UINT nPartLen = 64 - nIndex;
if (nInputLen >= nPartLen)
{
memcpy( &m_lpszBuffer[nIndex], Input, nPartLen );
Transform( m_lpszBuffer );
for (i = nPartLen; i + 63 < nInputLen; i += 64)
{
Transform( &Input[i] );
}
nIndex = 0;
}
else
{
i = 0;
}
// Buffer remaining input
memcpy( &m_lpszBuffer[nIndex], &Input[i], nInputLen-i);
}

加入這三個文件，就可以調用里面的重載函數，完成對字符串的加密工作和對文件名的加密工作等等。