c++builder CryptoAPI md5

#include <wincrypt.h>

DWORD GetHash(

    CONST BYTE * pbData,

    DWORD        dwDataLen,

    ALG_ID       algId,

    LPTSTR       pszHash )

{

    DWORD dwReturn = 0;

    HCRYPTPROV hProv;

    if ( !CryptAcquireContext( &hProv, NULL, NULL, PROV_RSA_FULL,

        CRYPT_VERIFYCONTEXT ) )

    {

        return ( dwReturn = GetLastError( ) );

    }



    HCRYPTHASH hHash;

    // Alg Id:CALG_MD5,CALG_SHA

    if ( !CryptCreateHash( hProv, algId, 0, 0, &hHash ) )

    {

        dwReturn = GetLastError( );

        CryptReleaseContext( hProv, 0 );

        return dwReturn;

    }



    if ( !CryptHashData( hHash, pbData, dwDataLen, 0 ) )

    {

        dwReturn = GetLastError( );

        CryptDestroyHash( hHash );

        CryptReleaseContext( hProv, 0 );

        return dwReturn;

    }



    DWORD dwSize;

    DWORD dwLen = sizeof( dwSize );

    CryptGetHashParam( hHash, HP_HASHSIZE, ( BYTE * )( & dwSize ), & dwLen, 0 );



    BYTE * pHash = new BYTE[ dwSize ];

    dwLen = dwSize;

    CryptGetHashParam( hHash, HP_HASHVAL, pHash, & dwLen, 0 );



    lstrcpy( pszHash, _T( "" ) );

    TCHAR szTemp[ 3 ];

    for ( DWORD i = 0; i < dwLen; ++i )

    {

        // wsprintf(szTemp, _T("%X%X"), pHash[i] >> 4, pHash[i] & 0xf);

        wsprintf( szTemp, L"%02X", pHash[ i ] );

        lstrcat( pszHash, szTemp );

    }

    delete[ ]pHash;



    CryptDestroyHash( hHash );

    CryptReleaseContext( hProv, 0 );

    return dwReturn;

}



void __fastcall TForm2::Button2Click( TObject * Sender )

{

    char szStr[ 20 ] =    {        0 } ;

    TCHAR szHash[ 41 ] = {    0    } ;



    strcpy( szStr, "ww" ); // wcscpy

    GetHash( ( BYTE * )szStr, strlen( szStr ), CALG_MD5, szHash );

    Caption = szHash;



    strcpy( szStr, "ww" ); // wcscpy

    GetHash( ( BYTE * )szStr, strlen( szStr ), CALG_MD5, szHash );

    Caption = szHash;

    //

    // strwcpy( szStr, "测试SHA" );

    // GetHash( ( BYTE * )szStr, strlen( szStr ), CALG_SHA, szHash );

    // MessageBox( NULL, szHash, szStr, MB_OK );

}

 

多数时候这个函数的dwProvType使用PROV_RSA_FULL（网上的开源代码基本都是使用这个常数），这对MD5，SHA-1等都有效；但是却不是正确的SHA-256/512的provider type，所以使用这个常数创建的context会在之后创建SHA-256/512算法时发生错误。

正确的做法是使用PROV_RSA_AES。

from http://blog.kingsamchen.com/archives/tag/sha