Шифрование симметричным ключом c++(CryptoAPI)

#pragma warning(disable : 4996)

#include <stdio.h>
#include <windows.h>
#include <wincrypt.h>
#include <iostream>
#include <string>

char        SysMessage[512];
HCRYPTPROV  hProv = 0;
HCRYPTKEY   hKey = 0;
BYTE        *pCryptBuf = 0;

char* GetSysMessage(DWORD errcode)
{
    FormatMessage(FORMAT_MESSAGE_FROM_SYSTEM
        | FORMAT_MESSAGE_IGNORE_INSERTS,    // don't use arguments
        NULL,                               // don't use format string
        errcode,                            // error code
        0,                                  // any language
        SysMessage, sizeof(SysMessage),     // message buffer
        NULL);                              // no additional arguments
    return(SysMessage);
}

void ErrorExit(int err)
{
    if (hKey)
        CryptDestroyKey(hKey);
    if (hProv)
        CryptReleaseContext(hProv, 0);
    if (pCryptBuf)
        free(pCryptBuf);

    system("pause");

    exit(err);
}

int main()
{
    char        *pSrcData;
    BOOL        bRes;
    DWORD       buflen;
    DWORD       datalen;

    // Acquire a handle to CSP
    bRes = CryptAcquireContext(
        &hProv,            // returned crypto-provider handle
        NULL,              // use default key container.
        MS_DEF_PROV,       // use default CSP.
        PROV_RSA_FULL,     // MS RSA provider (always presents)
        0);               // no special action.
    if (!bRes)
    {
        printf("CryptAcquireContext failed: %s\n", GetSysMessage(GetLastError()));
        //ErrorExit(1);
    }

    //  Create RC4 symmetrci key
    bRes = CryptGenKey(hProv,              // CSP handle
        CALG_RC4,           // RC4 algotrythm
        0 | CRYPT_NO_SALT,  // no "salt", no export, default length
        &hKey);
    if (!bRes)
    {
        printf("CryptGenKey failed: %s\n", GetSysMessage(GetLastError()));
        ErrorExit(1);
    }

    std::cout << "Please enter line to encrypt:\n";

    std::string message;
    std::getline(std::cin,message);

    // Determine buffer length
    pSrcData = (char *) (message.c_str());
    datalen = strlen(pSrcData);
    buflen = datalen;
    bRes = CryptEncrypt(hKey,
        0,          // no hash
        TRUE,       // "final" flag
        0,          // reserved
        NULL,       // calculate buffer size only
        &buflen,    // return size for ciphered text
        0);
    if (!bRes) {
        printf("CryptEncrypt (buffer size) failed: %s\n",
            GetSysMessage(GetLastError()));
        ErrorExit(1);
    }

    printf("text '%s' needs %d bytes for encryption buffer\n", pSrcData, buflen);

    // Encrypt
    pCryptBuf = (BYTE*)malloc(buflen);
    strncpy((char*)pCryptBuf, pSrcData, datalen);
    bRes = CryptEncrypt(hKey,
        0,          // no hash
        TRUE,       // "final" flag
        0,          // reserved
        pCryptBuf,  // buffer with data
        &datalen,   // return size for ciphered text
        buflen);
    if (!bRes) {
        printf("CryptEncrypt (encryption) failed: %s\n",
            GetSysMessage(GetLastError()));
        ErrorExit(1);
    }

    printf("encrypted text is '%.*s' (%d bytes)\n",
        datalen, pCryptBuf, datalen);

    // Decrypt back
    datalen = buflen;
    bRes = CryptDecrypt(hKey,
        0,
        TRUE,
        0,
        pCryptBuf,
        &datalen);
    if (!bRes) {
        printf("CryptDecrypt failed: %s\n",
            GetSysMessage(GetLastError()));
        ErrorExit(1);
    }

    printf("decrypted text is '%.*s'\n", datalen, pCryptBuf);


    // Cleanup
    ErrorExit(0);
}