以下示例演示如何使用 CryptoAPI 计算文件的内容的 MD5 哈希。 此示例对运行时指定的文件的内容执行计算。

#include <stdio.h>
#include <windows.h>
#include <Wincrypt.h>
#define BUFSIZE 1024
#define MD5LEN  16
DWORD main()
    DWORD dwStatus = 0;
    BOOL bResult = FALSE;
    HCRYPTPROV hProv = 0;
    HCRYPTHASH hHash = 0;
    HANDLE hFile = NULL;
    BYTE rgbFile[BUFSIZE];
    DWORD cbRead = 0;
    BYTE rgbHash[MD5LEN];
    DWORD cbHash = 0;
    CHAR rgbDigits[] = "0123456789abcdef";
    LPCWSTR filename=L"filename.txt";
    // Logic to check usage goes here.
    hFile = CreateFile(filename,
        GENERIC_READ,
        FILE_SHARE_READ,
        NULL,
        OPEN_EXISTING,
        FILE_FLAG_SEQUENTIAL_SCAN,
        NULL);
    if (INVALID_HANDLE_VALUE == hFile)
        dwStatus = GetLastError();
        printf("Error opening file %s\nError: %d\n", filename, 
            dwStatus); 
        return dwStatus;
    // Get handle to the crypto provider
    if (!CryptAcquireContext(&hProv,
        NULL,
        NULL,
        PROV_RSA_FULL,
        CRYPT_VERIFYCONTEXT))
        dwStatus = GetLastError();
        printf("CryptAcquireContext failed: %d\n", dwStatus); 
        CloseHandle(hFile);
        return dwStatus;
    if (!CryptCreateHash(hProv, CALG_MD5, 0, 0, &hHash))
        dwStatus = GetLastError();
        printf("CryptAcquireContext failed: %d\n", dwStatus); 
        CloseHandle(hFile);
        CryptReleaseContext(hProv, 0);
        return dwStatus;
    while (bResult = ReadFile(hFile, rgbFile, BUFSIZE, 
        &cbRead, NULL))
        if (0 == cbRead)
            break;
        if (!CryptHashData(hHash, rgbFile, cbRead, 0))
            dwStatus = GetLastError();
            printf("CryptHashData failed: %d\n", dwStatus); 
            CryptReleaseContext(hProv, 0);
            CryptDestroyHash(hHash);
            CloseHandle(hFile);
            return dwStatus;
    if (!bResult)
        dwStatus = GetLastError();
        printf("ReadFile failed: %d\n", dwStatus); 
        CryptReleaseContext(hProv, 0);
        CryptDestroyHash(hHash);
        CloseHandle(hFile);
        return dwStatus;
    cbHash = MD5LEN;
    if (CryptGetHashParam(hHash, HP_HASHVAL, rgbHash, &cbHash, 0))
        printf("MD5 hash of file %s is: ", filename);
        for (DWORD i = 0; i < cbHash; i++)
            printf("%c%c", rgbDigits[rgbHash[i] >> 4],
                rgbDigits[rgbHash[i] & 0xf]);
        printf("\n");
        dwStatus = GetLastError();
        printf("CryptGetHashParam failed: %d\n", dwStatus); 
    CryptDestroyHash(hHash);
    CryptReleaseContext(hProv, 0);
    CloseHandle(hFile);
    return dwStatus;