使用WinCrypt进行简单的对称加密实例

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2008年12月16日星期二

http://blog.csdn.net/lixiaomin_235/article/details/3532397

微软在wincrypt.h中定义了大量的加解密算法的API，方便了软件加解密的实现，可以使我们不必关注密码学的算法，就可以实现高效率的软件加密。下面通过一个类，对API实现简单的封装。详细代码如下：

头文件：MyCryptOpt.h

#pragma once

#include "windows.h"

#include "wincrypt.h"

#define MY_ENCODING_TYPE (PKCS_7_ASN_ENCODING | X509_ASN_ENCODING)

#define KEYLENGTH 0x00800000

#define ENCRYPT_ALGORITHM CALG_RC4

#define ENCRYPT_BLOCK_SIZE 8

class CMyCryptOpt

{

public:

CMyCryptOpt(void);

~CMyCryptOpt(void);

BOOL InitCrypt();

void DestroyCrypt();

BOOL MyEncryptFile(LPSTR lpSourceFile, LPSTR lpDestFile, LPSTR lpPassword);

BOOL MyDecryptFile(LPSTR lpSourceFile, LPSTR lpDestFile, LPSTR lpPassword);

protected:

BOOL CryptProcess(LPSTR lpSourceFile, LPSTR lpDestFile, LPSTR lpPassword);

private:

FILE *m_hSource;

FILE *m_hDestination;

HCRYPTPROV m_hCryptProv;

HCRYPTKEY m_hKey;

HCRYPTHASH m_hHash;

PBYTE m_pbBuffer;

DWORD m_dwBlockLen;

DWORD m_dwBufferLen;

DWORD m_dwCount;

};

源文件：MyCryptOpt.cpp

#include "StdAfx.h"

#include "MyCryptOpt.h"

CMyCryptOpt::CMyCryptOpt(void)

{

}

CMyCryptOpt::~CMyCryptOpt(void)

{

}

BOOL CMyCryptOpt::InitCrypt()

{

// 获得一个CSP句柄

if (!CryptAcquireContext(&m_hCryptProv,NULL,NULL,PROV_RSA_FULL,0))

{

if (!CryptAcquireContext(

&m_hCryptProv,

NULL,

PROV_RSA_FULL,

CRYPT_NEWKEYSET))

{

OutputDebugString("CryptAcquireContext() error!");

return FALSE;

}

// 创建一个会话密钥

if (!CryptCreateHash(

m_hCryptProv,

CALG_MD5,

&m_hHash))

{

OutputDebugString("CryptCreateHash() error!");

return FALSE;

}

return TRUE;

}

void CMyCryptOpt::DestroyCrypt()

{

// close files

if (m_hSource)

fclose(m_hSource);

if (m_hDestination)

fclose(m_hDestination);

// free memory

if (m_pbBuffer)

free(m_pbBuffer);

// destroy session key

if (m_hKey)

CryptDestroyKey(m_hKey);

// destroy hash object

CryptDestroyHash(m_hHash);

m_hHash = NULL;

// Release provider handle

if (m_hCryptProv)

CryptReleaseContext(m_hCryptProv,0);

}

BOOL CMyCryptOpt::MyEncryptFile(LPSTR lpSourceFile, LPSTR lpDestFile, LPSTR lpPassword)

{

// process for encrypt

if (!CryptProcess(lpSourceFile,lpDestFile,lpPassword))

return FALSE;

// 加密源文件，并将加密后数据写入目标文件

{

// read source file

m_dwCount = fread(m_pbBuffer,1,m_dwBlockLen,m_hSource);

if (ferror(m_hSource))

{

OutputDebugString("读写源文件错误!");

return FALSE;

}

// encrypt data

if (!CryptEncrypt(

m_hKey,

feof(m_hSource),

m_pbBuffer,

&m_dwCount,

m_dwBufferLen))

{

OutputDebugString("CryptEncrypt() failed!");

return FALSE;

}

// write data to file

fwrite(m_pbBuffer,1,m_dwCount,m_hDestination);

if (ferror(m_hDestination))

{

OutputDebugString("write file error!");

return FALSE;

}

while (!feof(m_hSource));

return TRUE;

}

BOOL CMyCryptOpt::MyDecryptFile(LPSTR lpSourceFile, LPSTR lpDestFile, LPSTR lpPassword)

{

// process for decrypt

if (!CryptProcess(lpSourceFile,lpDestFile,lpPassword))

return FALSE;

// 解密源文件，并将解密后数据写入目标文件

{

// read source file

m_dwCount = fread(m_pbBuffer,1,m_dwBlockLen,m_hSource);

if (ferror(m_hSource))

{

OutputDebugString("读写源文件错误!");

return FALSE;

}

// decrypt data

if (!CryptDecrypt(

m_hKey,

feof(m_hSource),

m_pbBuffer,

&m_dwCount))

{

OutputDebugString("CryptEncrypt() failed!");

return FALSE;

}

// write data to file

fwrite(m_pbBuffer,1,m_dwCount,m_hDestination);

if (ferror(m_hDestination))

{

OutputDebugString("write file error!");

return FALSE;

}

while (!feof(m_hSource));

return TRUE;

}

BOOL CMyCryptOpt::CryptProcess(LPSTR lpSourceFile, LPSTR lpDestFile, LPSTR lpPassword)

{

// 打开要加密的源文件

m_hSource = fopen(lpSourceFile,"rb");

if (!m_hSource)

{

OutputDebugString("open source file failed!");

return FALSE;

}

// 打开加密后产生的目标文件

m_hDestination = fopen(lpDestFile,"wb");

if (!m_hDestination)

{

OutputDebugString("open destination file failed!");

return FALSE;

}

// 用输入的密码产生一个散列

if (!CryptHashData(

m_hHash,

(BYTE*)lpPassword,

strlen(lpPassword),

0))

{

OutputDebugString("CryptHashData() failed!");

return FALSE;

}

// 通过散列生成会话密钥

if (!CryptDeriveKey(

m_hCryptProv,

ENCRYPT_ALGORITHM,

m_hHash,

KEYLENGTH,

&m_hKey))

{

OutputDebugString("CryptDeriveKey() failed!");

return FALSE;

}

// 因为加密算法是按ENCRYPT_BLOCK_SIZE 大小的块加密的，所以被加密的

// 数据长度必须是ENCRYPT_BLOCK_SIZE 的整数倍。下面计算一次加密的

// 数据长度。

m_dwBlockLen = 1000 - 1000 % ENCRYPT_BLOCK_SIZE;

// Determine the block size. If a block cipher is used,

// it must have room for an extra block.

if (ENCRYPT_BLOCK_SIZE > 1)

{

m_dwBufferLen = m_dwBlockLen + ENCRYPT_BLOCK_SIZE;

}

else

{

m_dwBufferLen = m_dwBlockLen;

}

// 为缓冲区分配内存

m_pbBuffer = (BYTE*)malloc(m_dwBufferLen);

if (!m_pbBuffer)

{

OutputDebugString("分配内存错误!");

return FALSE;

}

return TRUE;

}

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