[C++]md5 checksum of a string

[ᵁᴻᴷᴺᴼᵂᴻ]

char* __stdcall chksum_md5(char* stringforhash )
{
    //msdn
    int di; 
    HCRYPTPROV Provider = 0;
    ::CryptAcquireContext(&Provider,NULL,MS_DEF_PROV,PROV_RSA_FULL,CRYPT_VERIFYCONTEXT);

    HCRYPTHASH Hash = 0;
    ::CryptCreateHash(Provider,CALG_MD5,0,0,&Hash);
    ::CryptHashData(Hash,(unsigned char*)stringforhash,strlen(stringforhash), 0);

    unsigned char digest2[16];
    unsigned long size = sizeof(digest2);
    ::CryptGetHashParam(Hash, HP_HASHVAL, digest2, &size, 0);
    ::CryptDestroyHash(Hash);
    ::CryptReleaseContext(Provider, 0);

    char* hex_output = new char[33];     

    for( di = 0;  di < 16;  di++ )
        ::sprintf(hex_output + di * 2,"%02x", digest2[di]);

    return hex_output;
}