Question

C++ CryptGenRandom()函数的使用！急！

我现在的目的很简单，就是想利用这个函数来产生随机数。之前使用Rand()函数，但是发现这个函数并不能产生真正的随机数。求高手用CryptGenRandom函数给个产生随机数的示例！谢谢！

Answer 1

从MSDN上给你摘一段吧，没用过
#include <wincrypt.h>

HCRYPTPROV hProv = 0;
HCRYPTKEY hKey = 0;
DWORD dwMode;
BYTE pbData[16];
DWORD dwCount;
DWORD i;

// Get a handle to the user default provider using CryptAcquireContext.
// For sample code, see CryptAcquireContext.
...
...

// Create a random block cipher session key.
if(!CryptGenKey(hProv, CALG_RC2, CRYPT_EXPORTABLE, &hKey)) {
printf("Error %x during CryptGenKey!\n", GetLastError());
goto done;
}

// Set the cipher mode.
dwMode = CRYPT_MODE_ECB;
if(!CryptSetKeyParam(hKey, KP_MODE, &dwMode, 0)) {
printf("Error %x during CryptSetKeyParam!\n", GetLastError());
goto done;
}

// Generate a random initialization vector.
if(!CryptGenRandom(hProv, 8, pbData)) {
printf("Error %x during CryptGenRandom!\n", GetLastError());
goto done;
}

// Set the initialization vector.
if(!CryptSetKeyParam(hKey, KP_IV, pbData, 0)) {
printf("Error %x during CryptSetKeyParam!\n", GetLastError());
goto done;
}

// Use 'hKey' to encrypt a message.
...

done:

// Destroy the session key.
if(hKey != 0) CryptDestroyKey(hKey);

// Free the provider handle.
if(hProv != 0) CryptReleaseContext(hProv, 0);

Answer 2

rand函数需要先调用srand来生成随机数种子
如
#include<time.h>
srand(time(0));

后面再利用rand取随机数