範例 C 程式：設定和取得工作階段金鑰參數

下列範例會建立隨機工作階段金鑰、取得並列印該索引鍵的一些預設參數、在原始索引鍵上設定新的參數，然後取得並列印該新參數的值。 它會藉由終結工作階段金鑰並釋放密碼編譯內容來清除。

此範例說明如何使用下列工作和函式：

• 使用 CryptAcquireCoNtext存取 CSP。
• 使用 CryptGenRandom以隨機位元組提出緩衝區。
• 使用 CryptGenKey建立工作階段金鑰。
• 使用 CryptGetKeyParam取得金鑰參數的值。
• 使用 CryptSetKeyParam 來改變金鑰產生程式。
• 使用 CryptDestroyKey終結金鑰。
• 使用 CryptReleaseCoNtext釋放 CSP。

此範例使用 MyHandleError函式。 此函式的程式碼隨附于範例中。 此函式和其他輔助函式的程式碼也會列在常規用途 Functions底下。

//-------------------------------------------------------------------
// Copyright (C) Microsoft.  All rights reserved.

#include <windows.h>
#include <wincrypt.h>
#include <stdio.h>
#include <tchar.h>

// Link with the Crypt32.lib file.
#pragma comment (lib, "Crypt32")

void MyHandleError(PCTSTR psz);

void main()
{
    HCRYPTPROV hProv;
    HCRYPTKEY hKey;
    DWORD dwMode;
    BYTE pbData[16];
    BYTE pbRandomData[8];
    DWORD dwCount;
    DWORD i;

    // Acquire a cryptographic provider context handle.
    if(!CryptAcquireContext(
        &hProv, 
        NULL, 
        NULL, 
        PROV_RSA_FULL, 
        0)) 
    {
        MyHandleError(TEXT("Error during CryptAcquireContext."));
    }

    //  Generate eight bytes of random data into pbRandomData.
    if( CryptGenRandom(
            hProv,
            8,
            pbRandomData))
    {
        _tprintf(TEXT("Eight bytes of random data have been generated.\n"));
    }
    else
    {
        MyHandleError(TEXT("Random bytes were not correctly generated."));
    }

    // Create a random block cipher session key.
    if(!CryptGenKey(
            hProv, 
            CALG_RC4, 
            CRYPT_EXPORTABLE, 
            &hKey)) 
    {
        MyHandleError(TEXT("Error during CryptGenKey."));
    }

    // Read the cipher mode.
    dwCount = sizeof(DWORD);
    if(CryptGetKeyParam(
        hKey, 
        KP_MODE, 
        (PBYTE)&dwMode, 
        &dwCount, 
        0))
    {
        // Print the cipher mode.
        _tprintf(TEXT("Default cipher mode: %d\n"), dwMode);
    }
    else
    {
        MyHandleError(TEXT("Error during CryptGetKeyParam."));
    }

    // Read the initialization vector.

    //  Get the length of the initialization vector.
    if(!CryptGetKeyParam(
        hKey, 
        KP_IV, 
        NULL,     
        &dwCount, 
        0)) 
    {
        MyHandleError(TEXT("Error getting the IV length"));
    }

    // Get the initialization vector, itself.
    if(CryptGetKeyParam(
        hKey, 
        KP_IV, 
        pbData, 
        &dwCount, 
        0))
    {
        // Print the initialization vector.
        _tprintf(TEXT("Default IV:"));
        for(i = 0; i < dwCount; i++) 
        {
            _tprintf(TEXT("%2.2x "),pbData[i]);
        }

        _tprintf(TEXT("\n"));
    }
    else
    {
        MyHandleError(TEXT("Error getting the IV."));
    }

    //  Reset the initialization vector.
    if(CryptSetKeyParam(
        hKey,
        KP_IV,
        pbRandomData,
        0))
    {
        _tprintf(TEXT("New initialization vector is set.\n"));
    }
    else
    {
        MyHandleError(TEXT("The new IV was not set."));
    }

    // Read the new initialization vector.

    //  Get the length of the new initialization vector.
    if(!CryptGetKeyParam(
        hKey, 
        KP_IV, 
        NULL,     
        &dwCount, 
        0)) 
    {
        MyHandleError(TEXT("Error getting the IV length"));
    }

    // Get the initialization vector, itself.
    if(CryptGetKeyParam(
        hKey, 
        KP_IV, 
        pbData, 
        &dwCount, 
        0))
    {
        // Print the initialization vector.
        _tprintf(TEXT("RE-set IV:"));
        for(i = 0; i < dwCount; i++) 
        {
            _tprintf(TEXT("%2.2x "),pbData[i]);
        }
        
        _tprintf(TEXT("\n"));
    }
    else
    {
        MyHandleError(TEXT("Error getting the IV."));
    }

    //  Clean up.

    //  Destroy the session key.
    if(hKey)
    { 
        CryptDestroyKey(hKey);
    }

    // Release the provider handle.
    if(hProv)
    { 
        CryptReleaseContext(hProv, 0);
    }
} // End of main.

//-------------------------------------------------------------------
//    This example uses the function MyHandleError, a simple error
//    handling function, to print an error message to the standard  
//    error (stderr) file and exit the program. 
//    For most applications, replace this function with one 
//    that does more extensive error reporting.

void MyHandleError(PTSTR psz)
{
    _ftprintf(stderr, TEXT("An error occurred in the program. \n"));
    _ftprintf(stderr, TEXT("%s\n"), psz);
    _ftprintf(stderr, TEXT("Error number %x.\n"), GetLastError());
    _ftprintf(stderr, TEXT("Program terminating. \n"));
    exit(1);
} // End of MyHandleError.