示例 C 程序：创建和哈希会话密钥

以下示例创建一个会话密钥并对其进行哈希处理，该密钥可用于加密消息、文本或文件。

此示例还演示如何使用以下 CryptoAPI 函数：

• 用于获取加密服务提供程序的 CryptAcquireContext。
• CryptCreateHash 创建空哈希对象。
• 用于创建随机会话密钥的 CryptGenKey。
• CryptHashSessionKey 用于对创建的会话密钥进行哈希处理。
• CryptDestroyHash 以销毁哈希。
• CryptDestroyKey 用于销毁创建的密钥。
• CryptReleaseContext 用于释放 CSP。

此示例使用 函数 MyHandleError。 此示例中包含此函数的代码。 此函数和其他辅助函数的代码也列在常规用途函数下。

//  Copyright (C) Microsoft. All rights reserved.
//  
//  CreateAndHashSessionKey.cpp : Defines the entry point for the 
//  application.
//

#include <stdafx.h>

#include <stdio.h>
#include <windows.h>
#include <Wincrypt.h>

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

#define MY_ENCODING_TYPE  (PKCS_7_ASN_ENCODING | X509_ASN_ENCODING)

void MyHandleError(LPTSTR psz);

void main()
{
    HCRYPTPROV hCryptProv;
    HCRYPTHASH hHash;
    HCRYPTKEY hKey;

    //---------------------------------------------------------------
    // Acquire a cryptographic provider context handle.
    if(CryptAcquireContext(
        &hCryptProv, 
        NULL, 
        NULL, 
        PROV_RSA_FULL, 
        0)) 
    {
        printf("CryptAcquireContext complete. \n");
    }
    else
    {
        MyHandleError("Acquisition of context failed.");
    }

    //---------------------------------------------------------------
    // Create a hash object.
    if(CryptCreateHash(
        hCryptProv, 
        CALG_MD5, 
        0, 
        0, 
        &hHash)) 
    {
        printf("An empty hash object has been created. \n");
    }
    else
    {
        MyHandleError("Error during CryptBeginHash!\n");
    }

    //---------------------------------------------------------------
    // Create a random session key.
    if(CryptGenKey(
        hCryptProv, 
        CALG_RC2, 
        CRYPT_EXPORTABLE, 
        &hKey)) 
    {
        printf("A random session key has been created. \n");
    }
    else
    {
        MyHandleError("Error during CryptGenKey!\n");
    }

    //---------------------------------------------------------------
    // Compute the cryptographic hash on the key object.
    if(CryptHashSessionKey(
        hHash, 
        hKey, 
        0))
    {
        printf("The session key has been hashed. \n");
    }
    else
    {
        MyHandleError("Error during CryptHashSessionKey!\n");
    }

    /*
    Use the hash of the key object. For instance, additional data 
    could be hashed and sent in a message to several recipients. The 
    recipients will be able to verify who the message originator is 
    if the key used is also exported to them.
    */

    //---------------------------------------------------------------
    // Clean up.

    // Destroy the hash object.

    if(hHash)
    {
        if(!(CryptDestroyHash(hHash)))
        {
            MyHandleError("Error during CryptDestroyHash");
        }
    }

    // Destroy the session key.
    if(hKey)
    {
        if(!(CryptDestroyKey(hKey)))
        {
            MyHandleError("Error during CryptDestroyKey");
        }
    }

    // Release the provider.
    if(hCryptProv)
    {
        if(!(CryptReleaseContext(hCryptProv,0)))
        {
            MyHandleError("Error during CryptReleaseContext");
        }
    }
} // End main.

//  Define function MyHandleError.
void MyHandleError(LPTSTR 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.